feat: restore table UI with monolithic env var submission

Keep the original table-based UI with individual key/value rows,
edit/delete buttons, and add form. Use Alpine.js to manage the
env var list client-side. On form submit, all env vars are collected
into a hidden textarea field and POSTed as a single bulk request.

The server-side handler (HandleEnvVarSave) atomically replaces all
env vars: DELETE all existing + INSERT the full submitted set.

This combines the fix for issue #156 (env var 404) with the
monolithic list approach from issue #163.

closes #156
closes #163

templates/app_detail.html

@@ -101,14 +101,89 @@
     </div>
 
     <!-- Environment Variables -->
-    <div class="card p-6 mb-6">
+    <div class="card p-6 mb-6" x-data="{
+        vars: [],
+        newKey: '',
+        newValue: '',
+        init() {
+            const text = this.$refs.envVarsField.value;
+            if (!text.trim()) return;
+            this.vars = text.split('\n')
+                .map(l => l.trim())
+                .filter(l => l !== '')
+                .map(l => {
+                    const idx = l.indexOf('=');
+                    if (idx === -1) return null;
+                    return { key: l.substring(0, idx), value: l.substring(idx + 1), editing: false };
+                })
+                .filter(v => v !== null);
+        },
+        addVar() {
+            if (this.newKey.trim() === '') return;
+            this.vars.push({ key: this.newKey.trim(), value: this.newValue, editing: false });
+            this.newKey = '';
+            this.newValue = '';
+        },
+        removeVar(index) {
+            this.vars.splice(index, 1);
+        },
+        prepareSubmit() {
+            this.$refs.envVarsField.value = this.vars.map(v => v.key + '=' + v.value).join('\n');
+        }
+    }">
         <h2 class="section-title mb-4">Environment Variables</h2>
-        <form method="POST" action="/apps/{{.App.ID}}/env">
+        <form method="POST" action="/apps/{{.App.ID}}/env" @submit="prepareSubmit()">
             {{ .CSRFField }}
-            <p class="text-sm text-gray-500 mb-2">One <code>KEY=value</code> per line. Lines starting with <code>#</code> are ignored.</p>
+            <template x-if="vars.length > 0">
-            <textarea name="env_vars" rows="8" class="input font-mono text-sm w-full mb-2" placeholder="DATABASE_URL=postgres://localhost/mydb&#10;SECRET_KEY=changeme">{{range .EnvVars}}{{.Key}}={{.Value}}&#10;{{end}}</textarea>
+                <div class="overflow-x-auto mb-4">
+                    <table class="table">
+                        <thead class="table-header">
+                            <tr>
+                                <th>Key</th>
+                                <th>Value</th>
+                                <th class="text-right">Actions</th>
+                            </tr>
+                        </thead>
+                        <tbody class="table-body">
+                            <template x-for="(v, index) in vars" :key="index">
+                                <tr>
+                                    <template x-if="!v.editing">
+                                        <td class="font-mono font-medium" x-text="v.key"></td>
+                                    </template>
+                                    <template x-if="!v.editing">
+                                        <td class="font-mono text-gray-500" x-text="v.value"></td>
+                                    </template>
+                                    <template x-if="!v.editing">
+                                        <td class="text-right">
+                                            <button type="button" @click="v.editing = true" class="text-primary-600 hover:text-primary-800 text-sm mr-2">Edit</button>
+                                            <button type="button" @click="removeVar(index)" class="text-error-500 hover:text-error-700 text-sm">Delete</button>
+                                        </td>
+                                    </template>
+                                    <template x-if="v.editing">
+                                        <td colspan="3">
+                                            <div class="flex gap-2 items-center">
+                                                <input type="text" x-model="v.key" required class="input flex-1 font-mono text-sm">
+                                                <input type="text" x-model="v.value" required class="input flex-1 font-mono text-sm">
+                                                <button type="button" @click="v.editing = false" class="btn-primary text-sm">Done</button>
+                                            </div>
+                                            <p class="text-xs text-amber-600 mt-1">⚠ Container restart needed after env var changes.</p>
+                                        </td>
+                                    </template>
+                                </tr>
+                            </template>
+                        </tbody>
+                    </table>
+                </div>
+            </template>
+            <div class="flex flex-col sm:flex-row gap-2 mb-3">
+                <input type="text" x-model="newKey" placeholder="KEY" class="input flex-1 font-mono text-sm">
+                <input type="text" x-model="newValue" placeholder="value" class="input flex-1 font-mono text-sm">
+                <button type="button" @click="addVar()" class="btn-secondary">Add</button>
+            </div>
+            <textarea name="env_vars" x-ref="envVarsField" class="hidden">{{range .EnvVars}}{{.Key}}={{.Value}}
+{{end}}</textarea>
             <div class="flex items-center gap-3">
-                <button type="submit" class="btn-primary">Save Environment Variables</button>
+                <button type="submit" class="btn-primary">Save All</button>
                 <p class="text-xs text-amber-600">⚠ Container restart needed after env var changes.</p>
             </div>
         </form>