feat: add unified admin Marketplace Letzshop page

- Add new Marketplace section in admin sidebar with Letzshop sub-item
- Remove old Import and Letzshop Orders items from Product Catalog
- Create unified Letzshop management page with 3 tabs:
  - Products tab: Import/Export functionality
  - Orders tab: Order management with confirm/reject/tracking
  - Settings tab: API credentials and CSV URLs
- Add unified jobs table showing imports, exports, and order syncs
- Implement vendor autocomplete using Tom Select library (CDN + fallback)
- Add /vendors/{vendor_id}/jobs API endpoint for unified job listing
- Move database queries to service layer (LetzshopOrderService)
- Add LetzshopJobItem and LetzshopJobsListResponse schemas
- Include Tom Select CSS/JS assets as local fallback

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

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

models/schema/letzshop.py

@@ -332,3 +332,29 @@ class LetzshopVendorListResponse(BaseModel):
     total: int
     skip: int
     limit: int
+
+
+# ============================================================================
+# Jobs Schemas (Unified view of imports, exports, and syncs)
+# ============================================================================
+
+
+class LetzshopJobItem(BaseModel):
+    """Schema for a unified job item (import, export, or order sync)."""
+
+    id: int
+    type: str = Field(..., description="Job type: import, export, or order_sync")
+    status: str = Field(..., description="Job status")
+    created_at: datetime
+    started_at: datetime | None = None
+    completed_at: datetime | None = None
+    records_processed: int = 0
+    records_succeeded: int = 0
+    records_failed: int = 0
+
+
+class LetzshopJobsListResponse(BaseModel):
+    """Schema for paginated jobs list."""
+
+    jobs: list[LetzshopJobItem]
+    total: int