feat(client): 历史单明细优先读快照列、回退 product 关联

入库/出库明细 fromJson 改为优先取明细行自身的 product_code/name/series/spec
快照列，回退到 product 关联。历史导入单 product_id 为占位、无 product join，
靠快照列正常展示商品信息；App 新建单据仍走 product 关联，行为不变。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/models/stock_in.dart

@@ -34,7 +34,17 @@ class StockInItem {
     this.productStorage,
   });
 
-  factory StockInItem.fromJson(Map<String, dynamic> json) => StockInItem(
+  factory StockInItem.fromJson(Map<String, dynamic> json) {
+    final product = json['product'] as Map<String, dynamic>?;
+    // 历史导入行 product_id=0、无 product 关联，商品信息存在明细行自身列上。
+    // 优先取明细行快照列，回退到 product 关联（App 新建单据走 product）。
+    String? lineOrProduct(String lineKey, String productKey) {
+      final line = json[lineKey] as String?;
+      if (line != null && line.isNotEmpty) return line;
+      return product?[productKey] as String?;
+    }
+
+    return StockInItem(
         orderId: json['order_id'] != null
             ? (json['order_id'] as num).toInt()
             : null,
@@ -44,10 +54,10 @@ class StockInItem {
         totalPrice: (json['total_price'] as num).toDouble(),
         batchNo: json['batch_no'] as String?,
         productionDate: json['production_date'] as String?,
-        productName: (json['product'] as Map<String, dynamic>?)?['name'] as String?,
-        productCode: (json['product'] as Map<String, dynamic>?)?['code'] as String?,
-        productSeries: (json['product'] as Map<String, dynamic>?)?['series'] as String?,
-        productSpec: (json['product'] as Map<String, dynamic>?)?['spec'] as String?,
+        productName: lineOrProduct('product_name', 'name'),
+        productCode: lineOrProduct('product_code', 'code'),
+        productSeries: lineOrProduct('series', 'series'),
+        productSpec: lineOrProduct('spec', 'spec'),
         productUnit: (json['product'] as Map<String, dynamic>?)?['unit'] as String?,
         productOrigin: ((json['product'] as Map<String, dynamic>?)?['origin']
             as Map<String, dynamic>?)?['name'] as String?,
@@ -56,6 +66,7 @@ class StockInItem {
         productStorage: ((json['product'] as Map<String, dynamic>?)?['storage']
             as Map<String, dynamic>?)?['name'] as String?,
       );
+  }
 
   Map<String, dynamic> toJson() => {
         'product_id': productId,

client/lib/models/stock_out.dart

@@ -23,7 +23,17 @@ class StockOutItem {
     this.productUnit,
   });
 
-  factory StockOutItem.fromJson(Map<String, dynamic> json) => StockOutItem(
+  factory StockOutItem.fromJson(Map<String, dynamic> json) {
+    final product = json['product'] as Map<String, dynamic>?;
+    // 历史导入行 product_id=0、无 product 关联，商品信息存在明细行自身列上。
+    // 优先取明细行快照列，回退到 product 关联（App 新建单据走 product）。
+    String? lineOrProduct(String lineKey, String productKey) {
+      final line = json[lineKey] as String?;
+      if (line != null && line.isNotEmpty) return line;
+      return product?[productKey] as String?;
+    }
+
+    return StockOutItem(
         orderId: json['order_id'] != null
             ? (json['order_id'] as num).toInt()
             : null,
@@ -31,12 +41,13 @@ class StockOutItem {
         quantity: (json['quantity'] as num).toDouble(),
         unitPrice: (json['unit_price'] as num).toDouble(),
         totalPrice: (json['total_price'] as num).toDouble(),
-        productName: (json['product'] as Map<String, dynamic>?)?['name'] as String?,
-        productCode: (json['product'] as Map<String, dynamic>?)?['code'] as String?,
-        productSeries: (json['product'] as Map<String, dynamic>?)?['series'] as String?,
-        productSpec: (json['product'] as Map<String, dynamic>?)?['spec'] as String?,
+        productName: lineOrProduct('product_name', 'name'),
+        productCode: lineOrProduct('product_code', 'code'),
+        productSeries: lineOrProduct('series', 'series'),
+        productSpec: lineOrProduct('spec', 'spec'),
         productUnit: (json['product'] as Map<String, dynamic>?)?['unit'] as String?,
       );
+  }
 }
 
 class StockOutOrder {