feat: add Letzshop vendor directory with sync and admin management

- Add LetzshopVendorCache model to store cached vendor data from Letzshop API
- Create LetzshopVendorSyncService for syncing vendor directory
- Add Celery task for background vendor sync
- Create admin page at /admin/letzshop/vendor-directory with:
  - Stats dashboard (total, claimed, unclaimed vendors)
  - Searchable/filterable vendor list
  - "Sync Now" button to trigger sync
  - Ability to create platform vendors from Letzshop cache
- Add API endpoints for vendor directory management
- Add Pydantic schemas for API responses

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/routes/admin_pages.py

@@ -49,6 +49,7 @@ from app.api.deps import (
     get_current_admin_optional,
     get_db,
 )
+from app.core.config import settings
 from models.database.user import User
 
 router = APIRouter()
@@ -660,6 +661,7 @@ async def admin_background_tasks_page(
         {
             "request": request,
             "user": current_user,
+            "flower_url": settings.flower_url,
         },
     )
 
@@ -760,6 +762,38 @@ async def admin_letzshop_product_detail_page(
     )
 
 
+# ============================================================================
+# LETZSHOP VENDOR DIRECTORY
+# ============================================================================
+
+
+@router.get(
+    "/letzshop/vendor-directory",
+    response_class=HTMLResponse,
+    include_in_schema=False,
+)
+async def admin_letzshop_vendor_directory_page(
+    request: Request,
+    current_user: User = Depends(get_current_admin_from_cookie_or_header),
+    db: Session = Depends(get_db),
+):
+    """
+    Render Letzshop vendor directory management page.
+
+    Allows admins to:
+    - View cached Letzshop vendors
+    - Trigger manual sync from Letzshop API
+    - Create platform vendors from cached Letzshop vendors
+    """
+    return templates.TemplateResponse(
+        "admin/letzshop-vendor-directory.html",
+        {
+            "request": request,
+            "user": current_user,
+        },
+    )
+
+
 # ============================================================================
 # PRODUCT CATALOG ROUTES
 # ============================================================================