feat: implement core webhook engine, delivery system, and management UI (Phase 2)

- Webhook reception handler: look up entrypoint by UUID, verify active,
  capture full HTTP request (method, headers, body, content-type), create
  Event record, queue Delivery records for each active Target, return 200 OK.
  Handles edge cases: unknown UUID → 404, inactive → 410, oversized → 413.

- Delivery engine (internal/delivery): fx-managed background goroutine that
  polls for pending/retrying deliveries and dispatches to target type handlers.
  Graceful shutdown via context cancellation.

- Target type implementations:
  - HTTP: fire-and-forget POST with original headers forwarding
  - Retry: exponential backoff (1s, 2s, 4s...) up to max_retries
  - Database: immediate success (event already stored)
  - Log: slog output with event details

- Webhook management pages with Tailwind CSS + Alpine.js:
  - List (/sources): webhooks with entrypoint/target/event counts
  - Create (/sources/new): form with auto-created default entrypoint
  - Detail (/source/{id}): config, entrypoints, targets, recent events
  - Edit (/source/{id}/edit): name, description, retention_days
  - Delete (/source/{id}/delete): soft-delete with child records
  - Add Entrypoint (/source/{id}/entrypoints): inline form
  - Add Target (/source/{id}/targets): type-aware form
  - Event Log (/source/{id}/logs): paginated with delivery status

- Updated README: marked completed items, updated naming conventions
  table, added delivery engine to package layout and DI docs, updated
  column names to reflect entity rename.

- Rebuilt Tailwind CSS for new template classes.

Part of: #15

templates/source_detail.html

@@ -0,0 +1,154 @@
+{{template "base" .}}
+
+{{define "title"}}{{.Webhook.Name}} - Webhooker{{end}}
+
+{{define "content"}}
+<div class="max-w-6xl mx-auto px-6 py-8" x-data="{ showAddEntrypoint: false, showAddTarget: false }">
+    <div class="mb-6">
+        <a href="/sources" class="text-sm text-primary-600 hover:text-primary-700">&larr; Back to webhooks</a>
+        <div class="flex justify-between items-center mt-2">
+            <div>
+                <h1 class="text-2xl font-medium text-gray-900">{{.Webhook.Name}}</h1>
+                {{if .Webhook.Description}}
+                <p class="text-sm text-gray-500 mt-1">{{.Webhook.Description}}</p>
+                {{end}}
+            </div>
+            <div class="flex gap-2">
+                <a href="/source/{{.Webhook.ID}}/logs" class="btn-secondary">Event Log</a>
+                <a href="/source/{{.Webhook.ID}}/edit" class="btn-secondary">Edit</a>
+                <form method="POST" action="/source/{{.Webhook.ID}}/delete" onsubmit="return confirm('Delete this webhook and all its data?')">
+                    <button type="submit" class="btn-danger">Delete</button>
+                </form>
+            </div>
+        </div>
+    </div>
+
+    <div class="grid grid-cols-1 lg:grid-cols-2 gap-6">
+        <!-- Entrypoints -->
+        <div class="card">
+            <div class="p-4 border-b border-gray-200 flex justify-between items-center">
+                <h2 class="text-lg font-medium text-gray-900">Entrypoints</h2>
+                <button @click="showAddEntrypoint = !showAddEntrypoint" class="btn-text text-sm">
+                    <svg class="w-4 h-4 mr-1" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 4v16m8-8H4"/>
+                    </svg>
+                    Add
+                </button>
+            </div>
+
+            <!-- Add entrypoint form -->
+            <div x-show="showAddEntrypoint" x-cloak class="p-4 bg-gray-50 border-b border-gray-200">
+                <form method="POST" action="/source/{{.Webhook.ID}}/entrypoints" class="flex gap-2">
+                    <input type="text" name="description" placeholder="Description (optional)" class="input text-sm flex-1">
+                    <button type="submit" class="btn-primary text-sm">Add</button>
+                </form>
+            </div>
+
+            <div class="divide-y divide-gray-100">
+                {{range .Entrypoints}}
+                <div class="p-4">
+                    <div class="flex items-center justify-between mb-1">
+                        <span class="text-sm font-medium text-gray-900">{{if .Description}}{{.Description}}{{else}}Entrypoint{{end}}</span>
+                        {{if .Active}}
+                        <span class="badge-success">Active</span>
+                        {{else}}
+                        <span class="badge-error">Inactive</span>
+                        {{end}}
+                    </div>
+                    <code class="text-xs text-gray-500 break-all block mt-1">{{$.BaseURL}}/webhook/{{.Path}}</code>
+                </div>
+                {{else}}
+                <div class="p-4 text-sm text-gray-500">No entrypoints configured.</div>
+                {{end}}
+            </div>
+        </div>
+
+        <!-- Targets -->
+        <div class="card">
+            <div class="p-4 border-b border-gray-200 flex justify-between items-center">
+                <h2 class="text-lg font-medium text-gray-900">Targets</h2>
+                <button @click="showAddTarget = !showAddTarget" class="btn-text text-sm">
+                    <svg class="w-4 h-4 mr-1" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 4v16m8-8H4"/>
+                    </svg>
+                    Add
+                </button>
+            </div>
+
+            <!-- Add target form -->
+            <div x-show="showAddTarget" x-cloak class="p-4 bg-gray-50 border-b border-gray-200">
+                <form method="POST" action="/source/{{.Webhook.ID}}/targets" x-data="{ targetType: 'http' }" class="space-y-3">
+                    <div class="flex gap-2">
+                        <input type="text" name="name" placeholder="Target name" required class="input text-sm flex-1">
+                        <select name="type" x-model="targetType" class="input text-sm w-32">
+                            <option value="http">HTTP</option>
+                            <option value="retry">Retry</option>
+                            <option value="database">Database</option>
+                            <option value="log">Log</option>
+                        </select>
+                    </div>
+                    <div x-show="targetType === 'http' || targetType === 'retry'">
+                        <input type="url" name="url" placeholder="https://example.com/webhook" class="input text-sm">
+                    </div>
+                    <div x-show="targetType === 'retry'" class="flex gap-2 items-center">
+                        <label class="text-sm text-gray-700">Max retries:</label>
+                        <input type="number" name="max_retries" value="5" min="1" max="20" class="input text-sm w-24">
+                    </div>
+                    <button type="submit" class="btn-primary text-sm">Add Target</button>
+                </form>
+            </div>
+
+            <div class="divide-y divide-gray-100">
+                {{range .Targets}}
+                <div class="p-4">
+                    <div class="flex items-center justify-between mb-1">
+                        <span class="text-sm font-medium text-gray-900">{{.Name}}</span>
+                        <div class="flex items-center gap-2">
+                            <span class="badge-info">{{.Type}}</span>
+                            {{if .Active}}
+                            <span class="badge-success">Active</span>
+                            {{else}}
+                            <span class="badge-error">Inactive</span>
+                            {{end}}
+                        </div>
+                    </div>
+                    {{if .Config}}
+                    <code class="text-xs text-gray-500 break-all block mt-1">{{.Config}}</code>
+                    {{end}}
+                </div>
+                {{else}}
+                <div class="p-4 text-sm text-gray-500">No targets configured.</div>
+                {{end}}
+            </div>
+        </div>
+    </div>
+
+    <!-- Recent Events -->
+    <div class="card mt-6">
+        <div class="p-4 border-b border-gray-200 flex justify-between items-center">
+            <h2 class="text-lg font-medium text-gray-900">Recent Events</h2>
+            <a href="/source/{{.Webhook.ID}}/logs" class="btn-text text-sm">View All</a>
+        </div>
+        <div class="divide-y divide-gray-100">
+            {{range .Events}}
+            <div class="p-4">
+                <div class="flex items-center justify-between">
+                    <div class="flex items-center gap-3">
+                        <span class="badge-info">{{.Method}}</span>
+                        <span class="text-sm text-gray-500">{{.ContentType}}</span>
+                    </div>
+                    <span class="text-xs text-gray-400">{{.CreatedAt.Format "2006-01-02 15:04:05 UTC"}}</span>
+                </div>
+            </div>
+            {{else}}
+            <div class="p-8 text-center text-sm text-gray-500">No events received yet.</div>
+            {{end}}
+        </div>
+    </div>
+
+    <!-- Info -->
+    <div class="mt-4 text-sm text-gray-400">
+        <p>Retention: {{.Webhook.RetentionDays}} days &middot; Created: {{.Webhook.CreatedAt.Format "2006-01-02 15:04:05 UTC"}}</p>
+    </div>
+</div>
+{{end}}

templates/source_edit.html

@@ -0,0 +1,40 @@
+{{template "base" .}}
+
+{{define "title"}}Edit {{.Webhook.Name}} - Webhooker{{end}}
+
+{{define "content"}}
+<div class="max-w-2xl mx-auto px-6 py-8">
+    <div class="mb-6">
+        <a href="/source/{{.Webhook.ID}}" class="text-sm text-primary-600 hover:text-primary-700">&larr; Back to {{.Webhook.Name}}</a>
+        <h1 class="text-2xl font-medium text-gray-900 mt-2">Edit Webhook</h1>
+    </div>
+
+    <div class="card p-6">
+        {{if .Error}}
+        <div class="alert-error">{{.Error}}</div>
+        {{end}}
+
+        <form method="POST" action="/source/{{.Webhook.ID}}/edit" class="space-y-6">
+            <div class="form-group">
+                <label for="name" class="label">Name</label>
+                <input type="text" id="name" name="name" value="{{.Webhook.Name}}" required class="input">
+            </div>
+
+            <div class="form-group">
+                <label for="description" class="label">Description</label>
+                <textarea id="description" name="description" rows="3" class="input">{{.Webhook.Description}}</textarea>
+            </div>
+
+            <div class="form-group">
+                <label for="retention_days" class="label">Retention (days)</label>
+                <input type="number" id="retention_days" name="retention_days" value="{{.Webhook.RetentionDays}}" min="1" max="365" class="input">
+            </div>
+
+            <div class="flex gap-3">
+                <button type="submit" class="btn-primary">Save Changes</button>
+                <a href="/source/{{.Webhook.ID}}" class="btn-secondary">Cancel</a>
+            </div>
+        </form>
+    </div>
+</div>
+{{end}}

templates/source_logs.html

@@ -0,0 +1,61 @@
+{{template "base" .}}
+
+{{define "title"}}Event Log - {{.Webhook.Name}} - Webhooker{{end}}
+
+{{define "content"}}
+<div class="max-w-6xl mx-auto px-6 py-8">
+    <div class="mb-6">
+        <a href="/source/{{.Webhook.ID}}" class="text-sm text-primary-600 hover:text-primary-700">&larr; Back to {{.Webhook.Name}}</a>
+        <div class="flex justify-between items-center mt-2">
+            <h1 class="text-2xl font-medium text-gray-900">Event Log</h1>
+            <span class="text-sm text-gray-500">{{.TotalEvents}} total event{{if ne .TotalEvents 1}}s{{end}}</span>
+        </div>
+    </div>
+
+    <div class="card">
+        <div class="divide-y divide-gray-100">
+            {{range .Events}}
+            <div class="p-4" x-data="{ open: false }">
+                <div class="flex items-center justify-between cursor-pointer" @click="open = !open">
+                    <div class="flex items-center gap-3">
+                        <span class="badge-info">{{.Method}}</span>
+                        <span class="text-sm font-mono text-gray-700">{{.ID}}</span>
+                        <span class="text-sm text-gray-500">{{.ContentType}}</span>
+                    </div>
+                    <div class="flex items-center gap-4">
+                        {{range .Deliveries}}
+                        <span class="text-xs {{if eq .Status "delivered"}}text-green-600{{else if eq .Status "failed"}}text-red-600{{else if eq .Status "retrying"}}text-yellow-600{{else}}text-gray-400{{end}}">
+                            {{.Target.Name}}: {{.Status}}
+                        </span>
+                        {{end}}
+                        <span class="text-xs text-gray-400">{{.CreatedAt.Format "2006-01-02 15:04:05"}}</span>
+                        <svg class="w-4 h-4 text-gray-400 transition-transform" :class="{ 'rotate-180': open }" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7"/>
+                        </svg>
+                    </div>
+                </div>
+
+                <div x-show="open" x-cloak class="mt-3 p-3 bg-gray-50 rounded-md">
+                    <pre class="text-xs text-gray-700 overflow-x-auto whitespace-pre-wrap break-all">{{.Body}}</pre>
+                </div>
+            </div>
+            {{else}}
+            <div class="p-12 text-center text-sm text-gray-500">No events recorded yet.</div>
+            {{end}}
+        </div>
+    </div>
+
+    <!-- Pagination -->
+    {{if or .HasPrev .HasNext}}
+    <div class="flex justify-center gap-2 mt-6">
+        {{if .HasPrev}}
+        <a href="/source/{{.Webhook.ID}}/logs?page={{.PrevPage}}" class="btn-secondary text-sm">&larr; Previous</a>
+        {{end}}
+        <span class="inline-flex items-center px-4 py-2 text-sm text-gray-500">Page {{.Page}} of {{.TotalPages}}</span>
+        {{if .HasNext}}
+        <a href="/source/{{.Webhook.ID}}/logs?page={{.NextPage}}" class="btn-secondary text-sm">Next &rarr;</a>
+        {{end}}
+    </div>
+    {{end}}
+</div>
+{{end}}

templates/sources_list.html

@@ -0,0 +1,49 @@
+{{template "base" .}}
+
+{{define "title"}}Sources - Webhooker{{end}}
+
+{{define "content"}}
+<div class="max-w-6xl mx-auto px-6 py-8">
+    <div class="flex justify-between items-center mb-6">
+        <h1 class="text-2xl font-medium text-gray-900">Webhooks</h1>
+        <a href="/sources/new" class="btn-primary">
+            <svg class="w-5 h-5 mr-1" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 4v16m8-8H4"/>
+            </svg>
+            New Webhook
+        </a>
+    </div>
+
+    {{if .Webhooks}}
+    <div class="grid gap-4">
+        {{range .Webhooks}}
+        <a href="/source/{{.ID}}" class="card-elevated p-6 block">
+            <div class="flex justify-between items-start">
+                <div>
+                    <h2 class="text-lg font-medium text-gray-900">{{.Name}}</h2>
+                    {{if .Description}}
+                    <p class="text-sm text-gray-500 mt-1">{{.Description}}</p>
+                    {{end}}
+                </div>
+                <span class="badge-info">{{.RetentionDays}}d retention</span>
+            </div>
+            <div class="flex gap-6 mt-4 text-sm text-gray-500">
+                <span>{{.EntrypointCount}} entrypoint{{if ne .EntrypointCount 1}}s{{end}}</span>
+                <span>{{.TargetCount}} target{{if ne .TargetCount 1}}s{{end}}</span>
+                <span>{{.EventCount}} event{{if ne .EventCount 1}}s{{end}}</span>
+            </div>
+        </a>
+        {{end}}
+    </div>
+    {{else}}
+    <div class="card p-12 text-center">
+        <svg class="w-16 h-16 text-gray-300 mx-auto mb-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="1.5" d="M13.828 10.172a4 4 0 00-5.656 0l-4 4a4 4 0 105.656 5.656l1.102-1.101m-.758-4.899a4 4 0 005.656 0l4-4a4 4 0 00-5.656-5.656l-1.1 1.1"/>
+        </svg>
+        <h2 class="text-lg font-medium text-gray-900 mb-2">No webhooks yet</h2>
+        <p class="text-gray-500 mb-6">Create your first webhook to start receiving and forwarding events.</p>
+        <a href="/sources/new" class="btn-primary">Create Webhook</a>
+    </div>
+    {{end}}
+</div>
+{{end}}

templates/sources_new.html

@@ -0,0 +1,41 @@
+{{template "base" .}}
+
+{{define "title"}}New Webhook - Webhooker{{end}}
+
+{{define "content"}}
+<div class="max-w-2xl mx-auto px-6 py-8">
+    <div class="mb-6">
+        <a href="/sources" class="text-sm text-primary-600 hover:text-primary-700">&larr; Back to webhooks</a>
+        <h1 class="text-2xl font-medium text-gray-900 mt-2">Create Webhook</h1>
+    </div>
+
+    <div class="card p-6">
+        {{if .Error}}
+        <div class="alert-error">{{.Error}}</div>
+        {{end}}
+
+        <form method="POST" action="/sources/new" class="space-y-6">
+            <div class="form-group">
+                <label for="name" class="label">Name</label>
+                <input type="text" id="name" name="name" required autofocus placeholder="My Webhook" class="input">
+            </div>
+
+            <div class="form-group">
+                <label for="description" class="label">Description</label>
+                <textarea id="description" name="description" rows="3" placeholder="Optional description" class="input"></textarea>
+            </div>
+
+            <div class="form-group">
+                <label for="retention_days" class="label">Retention (days)</label>
+                <input type="number" id="retention_days" name="retention_days" value="30" min="1" max="365" class="input">
+                <p class="text-xs text-gray-500 mt-1">How long to keep event data.</p>
+            </div>
+
+            <div class="flex gap-3">
+                <button type="submit" class="btn-primary">Create Webhook</button>
+                <a href="/sources" class="btn-secondary">Cancel</a>
+            </div>
+        </form>
+    </div>
+</div>
+{{end}}