feat: implement boxing module with three modes (one2one, one2many, many2one)

- Add BoxInfoResult/BoxSaveResult data classes and API methods to ApiService
- Create BoxingPage with mode switching, auto-fill rules, duplicate detection
- Create BoxingDetailPage for read-only box detail view
- Activate boxing module in HomePage navigation

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

lib/pages/boxing_detail_page.dart

@@ -0,0 +1,95 @@
+import 'package:flutter/material.dart';
+import 'package:pad_scanner/services/api_service.dart';
+
+class BoxingDetailPage extends StatelessWidget {
+  final String paichanNo;
+  final List<BoxDetailData> existingBoxes;
+
+  const BoxingDetailPage({
+    super.key,
+    required this.paichanNo,
+    required this.existingBoxes,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Row(
+          children: [
+            const Text('装箱详情'),
+            const SizedBox(width: 12),
+            Text(
+              paichanNo,
+              style:
+                  const TextStyle(fontSize: 14, fontWeight: FontWeight.normal),
+            ),
+          ],
+        ),
+      ),
+      body: Column(
+        children: [
+          Expanded(
+            child: existingBoxes.isEmpty
+                ? const Center(child: Text('暂无装箱记录'))
+                : ListView.builder(
+                    padding: const EdgeInsets.all(12),
+                    itemCount: existingBoxes.length,
+                    itemBuilder: (context, index) {
+                      return _buildBoxGroup(context, existingBoxes[index]);
+                    },
+                  ),
+          ),
+          Container(
+            width: double.infinity,
+            padding: const EdgeInsets.symmetric(vertical: 12, horizontal: 16),
+            color: Theme.of(context).colorScheme.surfaceContainerHighest,
+            child: Text(
+              '共 ${existingBoxes.length} 箱',
+              style: const TextStyle(fontSize: 14),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildBoxGroup(BuildContext context, BoxDetailData box) {
+    return Padding(
+      padding: const EdgeInsets.only(bottom: 12),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text(
+            '箱号 ${box.boxNo}',
+            style: const TextStyle(fontSize: 14, fontWeight: FontWeight.bold),
+          ),
+          const SizedBox(height: 4),
+          Container(
+            width: double.infinity,
+            padding: const EdgeInsets.all(8),
+            decoration: BoxDecoration(
+              border: Border.all(color: Colors.grey.shade300),
+              borderRadius: BorderRadius.circular(6),
+            ),
+            child: Column(
+              children: box.items.map((item) {
+                return Padding(
+                  padding: const EdgeInsets.symmetric(vertical: 2),
+                  child: Row(
+                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                    children: [
+                      Text(item.zongpaiNo, style: const TextStyle(fontSize: 14)),
+                      Text('数量：${item.quantity}',
+                          style: const TextStyle(fontSize: 14)),
+                    ],
+                  ),
+                );
+              }).toList(),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}