feat: add marketplace products admin UI with copy-to-vendor functionality

- Add admin marketplace products page to browse imported products
- Add admin vendor products page to manage vendor catalog
- Add product detail pages for both marketplace and vendor products
- Implement copy-to-vendor API to copy marketplace products to vendor catalogs
- Add vendor product service with CRUD operations
- Update sidebar navigation with new product management links
- Add integration and unit tests for new endpoints and services

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/routes/admin_pages.py

@@ -25,6 +25,8 @@ Routes:
 - GET /users         → User management page (auth required)
 - GET /customers     → Customer management page (auth required)
 - GET /imports       → Import history page (auth required)
+- GET /marketplace-products → Marketplace products catalog (auth required)
+- GET /vendor-products → Vendor products catalog (auth required)
 - GET /settings      → Settings page (auth required)
 - GET /platform-homepage → Platform homepage manager (auth required)
 - GET /content-pages → Content pages list (auth required)
@@ -517,6 +519,99 @@ async def admin_marketplace_page(
     )
 
 
+# ============================================================================
+# PRODUCT CATALOG ROUTES
+# ============================================================================
+
+
+@router.get("/marketplace-products", response_class=HTMLResponse, include_in_schema=False)
+async def admin_marketplace_products_page(
+    request: Request,
+    current_user: User = Depends(get_current_admin_from_cookie_or_header),
+    db: Session = Depends(get_db),
+):
+    """
+    Render marketplace products page.
+    Browse the master product repository imported from external sources.
+    """
+    return templates.TemplateResponse(
+        "admin/marketplace-products.html",
+        {
+            "request": request,
+            "user": current_user,
+        },
+    )
+
+
+@router.get(
+    "/marketplace-products/{product_id}",
+    response_class=HTMLResponse,
+    include_in_schema=False,
+)
+async def admin_marketplace_product_detail_page(
+    request: Request,
+    product_id: int = Path(..., description="Marketplace Product ID"),
+    current_user: User = Depends(get_current_admin_from_cookie_or_header),
+    db: Session = Depends(get_db),
+):
+    """
+    Render marketplace product detail page.
+    Shows full product information from the master repository.
+    """
+    return templates.TemplateResponse(
+        "admin/marketplace-product-detail.html",
+        {
+            "request": request,
+            "user": current_user,
+            "product_id": product_id,
+        },
+    )
+
+
+@router.get("/vendor-products", response_class=HTMLResponse, include_in_schema=False)
+async def admin_vendor_products_page(
+    request: Request,
+    current_user: User = Depends(get_current_admin_from_cookie_or_header),
+    db: Session = Depends(get_db),
+):
+    """
+    Render vendor products catalog page.
+    Browse vendor-specific product catalogs with override capability.
+    """
+    return templates.TemplateResponse(
+        "admin/vendor-products.html",
+        {
+            "request": request,
+            "user": current_user,
+        },
+    )
+
+
+@router.get(
+    "/vendor-products/{product_id}",
+    response_class=HTMLResponse,
+    include_in_schema=False,
+)
+async def admin_vendor_product_detail_page(
+    request: Request,
+    product_id: int = Path(..., description="Vendor Product ID"),
+    current_user: User = Depends(get_current_admin_from_cookie_or_header),
+    db: Session = Depends(get_db),
+):
+    """
+    Render vendor product detail page.
+    Shows full product information with vendor-specific overrides.
+    """
+    return templates.TemplateResponse(
+        "admin/vendor-product-detail.html",
+        {
+            "request": request,
+            "user": current_user,
+            "product_id": product_id,
+        },
+    )
+
+
 # ============================================================================
 # SETTINGS ROUTES
 # ============================================================================