Initial commit with server startup infrastructure

Core infrastructure:
- Uber fx dependency injection
- Chi router with middleware stack
- SQLite database with embedded migrations
- Embedded templates and static assets
- Structured logging with slog

Features implemented:
- Authentication (login, logout, session management, argon2id hashing)
- App management (create, edit, delete, list)
- Deployment pipeline (clone, build, deploy, health check)
- Webhook processing for Gitea
- Notifications (ntfy, Slack)
- Environment variables, labels, volumes per app
- SSH key generation for deploy keys

Server startup:
- Server.Run() starts HTTP server on configured port
- Server.Shutdown() for graceful shutdown
- SetupRoutes() wires all handlers with chi router

templates/login.html

@@ -0,0 +1,50 @@
+{{template "base" .}}
+
+{{define "title"}}Login - upaas{{end}}
+
+{{define "content"}}
+<div class="min-h-screen flex items-center justify-center py-12 px-4">
+    <div class="max-w-md w-full">
+        <div class="text-center mb-8">
+            <h1 class="text-3xl font-medium text-gray-900">upaas</h1>
+            <p class="mt-2 text-gray-600">Sign in to continue</p>
+        </div>
+
+        <div class="card p-8">
+            {{template "alert-error" .}}
+
+            <form method="POST" action="/login" class="space-y-6">
+                <div class="form-group">
+                    <label for="username" class="label">Username</label>
+                    <input
+                        type="text"
+                        id="username"
+                        name="username"
+                        value="{{.Username}}"
+                        required
+                        autofocus
+                        autocomplete="username"
+                        class="input"
+                    >
+                </div>
+
+                <div class="form-group">
+                    <label for="password" class="label">Password</label>
+                    <input
+                        type="password"
+                        id="password"
+                        name="password"
+                        required
+                        autocomplete="current-password"
+                        class="input"
+                    >
+                </div>
+
+                <button type="submit" class="btn-primary w-full py-3">
+                    Sign In
+                </button>
+            </form>
+        </div>
+    </div>
+</div>
+{{end}}