feat(hosting): add Build POC button with template selector on site detail

Draft sites with a linked prospect show a "Build POC from Template"
section with:
- Template dropdown (generic, restaurant, construction, auto-parts,
  professional-services) loaded from /admin/hosting/sites/templates API
- "Build POC" button that calls POST /admin/hosting/sites/poc/build
- Loading state + success message with pages created count
- Auto-refreshes site detail after build (status changes to POC_READY)

Visible only for draft sites with a prospect_id.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/hosting/templates/hosting/admin/site-detail.html

@@ -39,6 +39,29 @@
         </div>
     </div>
 
+    <!-- Build POC (draft sites only) -->
+    <div x-show="site.status === 'draft' && site.prospect_id" class="p-4 bg-white rounded-lg shadow-xs dark:bg-gray-800">
+        <h3 class="text-sm font-semibold text-gray-700 dark:text-gray-300 mb-3">Build POC from Template</h3>
+        <div class="flex flex-wrap items-end gap-3">
+            <div class="flex-1 min-w-[200px]">
+                <select x-model="selectedTemplate"
+                        class="w-full px-3 py-2 text-sm border border-gray-300 dark:border-gray-600 rounded-lg focus:border-teal-400 focus:outline-none dark:bg-gray-700 dark:text-gray-300">
+                    <option value="">Select a template...</option>
+                    <template x-for="t in templates" :key="t.id">
+                        <option :value="t.id" x-text="t.name + ' — ' + t.description"></option>
+                    </template>
+                </select>
+            </div>
+            <button type="button" @click="buildPoc()" :disabled="!selectedTemplate || buildingPoc"
+                    class="inline-flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-teal-600 border border-transparent rounded-lg hover:bg-teal-700 focus:outline-none disabled:opacity-50">
+                <span x-show="!buildingPoc" x-html="$icon('sparkles', 'w-4 h-4 mr-2')"></span>
+                <span x-show="buildingPoc" x-html="$icon('spinner', 'w-4 h-4 mr-2')"></span>
+                <span x-text="buildingPoc ? 'Building...' : 'Build POC'"></span>
+            </button>
+        </div>
+        <p x-show="pocResult" class="mt-2 text-sm text-green-600" x-text="pocResult"></p>
+    </div>
+
     <!-- Lifecycle Actions -->
     <div class="flex flex-wrap gap-3 p-4 bg-white rounded-lg shadow-xs dark:bg-gray-800">
         <button type="button" x-show="site.status === 'draft'" @click="doAction('mark-poc-ready')"
@@ -307,7 +330,39 @@ function hostingSiteDetail(siteId) {
         acceptMerchantId: '',
         goLiveDomain: '',
         newService: { service_type: 'domain', name: '', price_cents: null, billing_period: 'monthly' },
-        async init() { await this.loadSite(); },
+        // POC builder
+        templates: [],
+        selectedTemplate: '',
+        buildingPoc: false,
+        pocResult: '',
+        async init() {
+            await this.loadSite();
+            await this.loadTemplates();
+        },
+        async loadTemplates() {
+            try {
+                var resp = await apiClient.get('/admin/hosting/sites/templates');
+                this.templates = resp.templates || [];
+            } catch (e) { /* ignore */ }
+        },
+        async buildPoc() {
+            if (!this.selectedTemplate || !this.site.prospect_id) return;
+            this.buildingPoc = true;
+            this.pocResult = '';
+            try {
+                var result = await apiClient.post('/admin/hosting/sites/poc/build', {
+                    prospect_id: this.site.prospect_id,
+                    template_id: this.selectedTemplate,
+                });
+                this.pocResult = 'POC built! ' + result.pages_created + ' pages created.';
+                Utils.showToast('POC built successfully', 'success');
+                await this.loadSite();
+            } catch (e) {
+                Utils.showToast('Build failed: ' + e.message, 'error');
+            } finally {
+                this.buildingPoc = false;
+            }
+        },
         async loadSite() {
             this.loading = true;
             this.error = null;