feat: add vendor order detail page with invoice integration

- Add new route /vendor/{code}/orders/{order_id} for order details
- Create order-detail.html template with:
  - Order summary with status and totals
  - Order items with per-item shipment status and ship buttons
  - Customer and shipping address display
  - Invoice section (create invoice or view existing)
  - Quick actions (confirm, ship all, mark delivered, cancel)
  - Status update modal with tracking info fields
  - Ship all modal for bulk shipment with tracking
- Create order-detail.js with full functionality:
  - Load order details, shipment status, and linked invoice
  - Individual item shipping with partial shipment support
  - Ship all remaining items with tracking info
  - Create invoice from order
  - Download invoice PDF
  - Status management with automatic shipment handling
- Update orders list to navigate to detail page instead of modal
- Add partially_shipped status (orange) to orders list

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

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

app/routes/vendor_pages.py

@@ -243,6 +243,40 @@ async def vendor_orders_page(
     )
 
 
+@router.get(
+    "/{vendor_code}/orders/{order_id}",
+    response_class=HTMLResponse,
+    include_in_schema=False,
+)
+async def vendor_order_detail_page(
+    request: Request,
+    vendor_code: str = Path(..., description="Vendor code"),
+    order_id: int = Path(..., description="Order ID"),
+    current_user: User = Depends(get_current_vendor_from_cookie_or_header),
+):
+    """
+    Render order detail page.
+
+    Shows comprehensive order information including:
+    - Order header and status
+    - Customer and shipping details
+    - Order items with shipment status
+    - Invoice creation/viewing
+    - Partial shipment controls
+
+    JavaScript loads order details via API.
+    """
+    return templates.TemplateResponse(
+        "vendor/order-detail.html",
+        {
+            "request": request,
+            "user": current_user,
+            "vendor_code": vendor_code,
+            "order_id": order_id,
+        },
+    )
+
+
 # ============================================================================
 # CUSTOMER MANAGEMENT
 # ============================================================================