feat(android): add attachment pending banner on boxing page

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

lib/pages/boxing_page.dart

@@ -118,6 +118,10 @@ class _BoxingPageState extends State<BoxingPage> with WidgetsBindingObserver {
   // ignore: unused_field -- already boxed qty for this category (later task)
   int? _attachmentBoxedQty;
 
+  /// Whether to show the attachment-pending banner.
+  bool _attachmentPending = false;
+  int _attachmentPendingCount = 0;
+
   @override
   void initState() {
     super.initState();
@@ -265,6 +269,8 @@ class _BoxingPageState extends State<BoxingPage> with WidgetsBindingObserver {
     _attachmentCategoryName = null;
     _attachmentExpectedQty = null;
     _attachmentBoxedQty = null;
+    _attachmentPending = false;
+    _attachmentPendingCount = 0;
   }
 
   // === 重复箱号检测 ===
@@ -388,6 +394,8 @@ class _BoxingPageState extends State<BoxingPage> with WidgetsBindingObserver {
               remainingQuantity: _remainingQuantity,
               zongpaiNo: _zongpaiNo,
               completedJumpBoxNo: _completedJumpBoxNo,
+              attachmentPending: _attachmentPending,
+              attachmentPendingCount: _attachmentPendingCount,
               onJumpToCompletedBox: () => this._jumpToCompletedBox(),
             ),