feat(hosting): add industry template infrastructure (Workstream 3B)

5 industry templates as JSON presets, each with theme + multi-page content:
- generic: clean minimal (homepage, about, contact)
- restaurant: warm tones, Playfair Display (homepage, about, menu, contact)
- construction: amber/earth tones, Montserrat (homepage, services, projects, contact)
- auto-parts: red/bold, parts-focused (homepage, catalog, contact)
- professional-services: navy/blue, Merriweather (homepage, services, team, contact)

Each template has:
- meta.json (name, description, tags, languages)
- theme.json (colors, fonts, layout, header style)
- pages/*.json (section-based homepage + content pages with i18n)
- {{placeholder}} variables for prospect data injection

TemplateService loads from templates_library/ directory with caching.
GET /admin/hosting/sites/templates endpoint to list available templates.

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

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

@@ -22,13 +22,26 @@ from app.modules.hosting.schemas.hosted_site import (
     HostedSiteUpdate,
     SendProposalRequest,
 )
+from app.modules.hosting.schemas.template import TemplateListResponse, TemplateResponse
 from app.modules.hosting.services.hosted_site_service import hosted_site_service
+from app.modules.hosting.services.template_service import template_service
 from app.modules.tenancy.schemas.auth import UserContext
 
 router = APIRouter(prefix="/sites")
 logger = logging.getLogger(__name__)
 
 
+@router.get("/templates", response_model=TemplateListResponse)
+def list_templates(
+    current_admin: UserContext = Depends(get_current_admin_api),
+):
+    """List available industry templates for POC site generation."""
+    templates = template_service.list_templates()
+    return TemplateListResponse(
+        templates=[TemplateResponse(**t) for t in templates],
+    )
+
+
 def _to_response(site) -> HostedSiteResponse:
     """Convert a hosted site model to response schema."""
     return HostedSiteResponse(