Add boxes/crates management system to warehouse module

- Created boxes_crates table with 8-digit auto-generated box numbers
- Added manage_boxes route and full CRUD operations
- Implemented box status tracking (open/closed)
- Added location assignment functionality
- Integrated QZ Tray printing with barcode labels
- Created manage_boxes.html with table, preview, and print features
- Added 'Manage Boxes/Crates' card to warehouse main page
- Boxes can be created without location and assigned later
- Includes delete functionality for admin/management roles
- Added box statistics display

py_app/app/templates/main_page_warehouse.html

@@ -23,7 +23,14 @@
             <a href="{{ url_for('warehouse.create_locations') }}" class="btn">Go to Locations</a>
         </div>
 
-        <!-- Card 3: Warehouse Reports -->
+        <!-- Card 3: Manage Boxes/Crates -->
+        <div class="dashboard-card">
+            <h3>Manage Boxes/Crates</h3>
+            <p>Track and manage boxes and crates in the warehouse.</p>
+            <a href="{{ url_for('warehouse.manage_boxes') }}" class="btn">Go to Boxes</a>
+        </div>
+
+        <!-- Card 4: Warehouse Reports -->
         <div class="dashboard-card">
             <h3>Warehouse Reports</h3>
             <p>View and export warehouse activity and inventory reports.</p>