feat: 完成7项功能任务

后端：
- fix(backend): InventoryLog 增加 Product/Warehouse 关联，Logs 接口加 Preload 修复流水记录显示"-"
- feat(backend): 新增 /inventory/batches 批次追踪接口
- feat(backend): 新增财务记录、编号规则接口（finance、number_rule handler）
- fix(backend): service/stock_test.go 修复 model.Date 类型错误

前端：
- feat(client): 入库/出库管理 Tab 调换顺序（审核在前），审核 Tab 加新建按钮，列表 Tab 无按钮
- feat(client): 入库单/出库单增加详情弹窗，显示完整单据信息和商品明细
- feat(client): 完善出库单新建表单（StockOutFormScreen），支持选客户/仓库/商品
- fix(client): StockInItem/StockOutItem.fromJson 修复读取嵌套 product 对象而非平铺字段
- feat(client): 批次追踪页面（BatchTrackingScreen）及侧边栏入口
- feat(client): 财务管理、盘点、编号规则接入真实后端 API
- fix(client): 入库/出库审核通过后 invalidate inventoryListProvider 刷新库存

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

client/lib/models/inventory.dart

@@ -43,6 +43,61 @@ class Inventory {
   }
 }
 
+// 批次追踪：已审核入库单的明细行
+class BatchRecord {
+  final int id;
+  final int productId;
+  final String? productName;
+  final String? productCode;
+  final String? productSpec;
+  final String? productUnit;
+  final String? batchNo;
+  final double quantity;
+  final double unitPrice;
+  final String? orderNo;
+  final String? orderDate;
+  final String? warehouseName;
+  final String? supplierName;
+
+  const BatchRecord({
+    required this.id,
+    required this.productId,
+    this.productName,
+    this.productCode,
+    this.productSpec,
+    this.productUnit,
+    this.batchNo,
+    required this.quantity,
+    required this.unitPrice,
+    this.orderNo,
+    this.orderDate,
+    this.warehouseName,
+    this.supplierName,
+  });
+
+  factory BatchRecord.fromJson(Map<String, dynamic> json) {
+    final product = json['product'] as Map<String, dynamic>?;
+    final order = json['order'] as Map<String, dynamic>?;
+    final warehouse = order?['warehouse'] as Map<String, dynamic>?;
+    final partner = order?['partner'] as Map<String, dynamic>?;
+    return BatchRecord(
+      id: (json['id'] as num).toInt(),
+      productId: (json['product_id'] as num).toInt(),
+      productName: product?['name'] as String?,
+      productCode: product?['code'] as String?,
+      productSpec: product?['spec'] as String?,
+      productUnit: product?['unit'] as String?,
+      batchNo: json['batch_no'] as String?,
+      quantity: (json['quantity'] as num).toDouble(),
+      unitPrice: (json['unit_price'] as num).toDouble(),
+      orderNo: order?['order_no'] as String?,
+      orderDate: order?['order_date'] as String?,
+      warehouseName: warehouse?['name'] as String?,
+      supplierName: partner?['name'] as String?,
+    );
+  }
+}
+
 class InventoryLog {
   final int warehouseId;
   final String? warehouseName;