feat: implement product search, media library, and vendor customers

- Add full-text product search in ProductService.search_products()
  searching titles, descriptions, SKUs, brands, and GTINs
- Implement complete vendor media library with file uploads,
  thumbnails, folders, and product associations
- Implement vendor customers API with listing, details, orders,
  statistics, and status management
- Add shop search results UI with pagination and add-to-cart
- Add vendor media library UI with drag-drop upload and grid view
- Add database migration for media_files and product_media tables
- Update TODO file with current launch status (~95% complete)

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

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

models/database/vendor.py

@@ -238,6 +238,13 @@ class Vendor(Base, TimestampMixin):
         cascade="all, delete-orphan",
     )
 
+    # Media library (one-to-many)
+    media_files = relationship(
+        "MediaFile",
+        back_populates="vendor",
+        cascade="all, delete-orphan",
+    )
+
     def __repr__(self):
         """String representation of the Vendor object."""
         return f"<Vendor(id={self.id}, vendor_code='{self.vendor_code}', name='{self.name}', subdomain='{self.subdomain}')>"