fix(hosting): POC builder works with existing sites

The Build POC button on site detail now passes site_id to the POC
builder, which populates the existing site's store with CMS content
instead of trying to create a new site (which failed with duplicate
slug error).

- poc_builder_service.build_poc() accepts optional site_id param
- If site_id given: uses existing site, skips hosted_site_service.create()
- If not given: creates new site (standalone POC build)
- API schema: added site_id to BuildPocRequest
- Frontend: passes this.site.id in the build request

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

app/modules/hosting/routes/api/admin_sites.py

@@ -75,6 +75,7 @@ class BuildPocRequest(BaseModel):
     prospect_id: int
     template_id: str
     merchant_id: int | None = None
+    site_id: int | None = None  # If set, populate existing site instead of creating new one
 
 
 class BuildPocResponse(BaseModel):
@@ -100,6 +101,7 @@ def build_poc(
         prospect_id=data.prospect_id,
         template_id=data.template_id,
         merchant_id=data.merchant_id,
+        site_id=data.site_id,
     )
     db.commit()
     return BuildPocResponse(**result)

app/modules/hosting/services/poc_builder_service.py

@@ -35,9 +35,13 @@ class PocBuilderService:
         prospect_id: int,
         template_id: str,
         merchant_id: int | None = None,
+        site_id: int | None = None,
     ) -> dict:
         """Build a complete POC site from prospect data and a template.
 
+        If site_id is given, populates the existing site's store with CMS
+        content. Otherwise creates a new HostedSite + Store.
+
         Returns dict with hosted_site, store, pages_created, theme_applied.
         """
         from app.modules.prospecting.models import Prospect
@@ -57,17 +61,19 @@ class PocBuilderService:
         # 3. Build placeholder context from prospect data
         context = self._build_context(prospect)
 
-        # 4. Create HostedSite + Store
+        # 4. Use existing site or create new one
+        if site_id:
+            site = hosted_site_service.get_by_id(db, site_id)
+        else:
             site_data = {
                 "business_name": context["business_name"],
-            "domain_name": prospect.domain_name,  # used for clean subdomain slug
+                "domain_name": prospect.domain_name,
                 "prospect_id": prospect_id,
                 "contact_email": context.get("email"),
                 "contact_phone": context.get("phone"),
             }
             if merchant_id:
                 site_data["merchant_id"] = merchant_id
-
             site = hosted_site_service.create(db, site_data)
 
         # 5. Get the hosting platform_id from the store

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

@@ -351,6 +351,7 @@ function hostingSiteDetail(siteId) {
                 var result = await apiClient.post('/admin/hosting/sites/poc/build', {
                     prospect_id: this.site.prospect_id,
                     template_id: this.selectedTemplate,
+                    site_id: this.site.id,
                 });
                 this.pocResult = 'POC built! ' + result.pages_created + ' pages created.';
                 Utils.showToast('POC built successfully', 'success');