feat: extend boxing page for accessory boxing support

Add pending accessories section to both single-code and multi-code boxing
modes. Accessories display with orange styling and a "加入本箱" button that
calls saveBoxRecord with item_type=accessory. Extend API service with
PendingAccessory model, itemType fields on data classes, and optional
accessory_id parameter on saveBoxRecord. Show accessories with visual
indicator (wrench icon + orange background) in boxing detail page.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/pages/boxing_detail_page.dart

@@ -103,15 +103,40 @@ class BoxingDetailPage extends StatelessWidget {
             ),
             child: Column(
               children: box.items.map((item) {
-                return Padding(
-                  padding: const EdgeInsets.symmetric(vertical: 2),
+                final isAccessory = item.itemType == 'accessory';
+                return Container(
+                  padding: const EdgeInsets.symmetric(
+                    vertical: 4,
+                    horizontal: 4,
+                  ),
+                  margin: const EdgeInsets.symmetric(vertical: 1),
+                  decoration: isAccessory
+                      ? BoxDecoration(
+                          color: Colors.orange.shade50,
+                          borderRadius: BorderRadius.circular(4),
+                        )
+                      : null,
                   child: Row(
                     children: [
+                      if (isAccessory)
+                        Padding(
+                          padding: const EdgeInsets.only(right: 6),
+                          child: Icon(
+                            Icons.build,
+                            size: 14,
+                            color: Colors.orange.shade700,
+                          ),
+                        ),
                       Expanded(
                         flex: 3,
                         child: Text(
                           item.zongpaiNo,
-                          style: const TextStyle(fontSize: 14),
+                          style: TextStyle(
+                            fontSize: 14,
+                            fontWeight: isAccessory
+                                ? FontWeight.w600
+                                : FontWeight.normal,
+                          ),
                           overflow: TextOverflow.ellipsis,
                         ),
                       ),