feat(client): Phase 2 库存屏照原型重建（去tab/KPI货值/库存·成本价·单价列）

照原型 inventory.html 把库存屏从「3 tab」重排为单视图：
- 去 3 tab（库存查询/预警/流水）→ 单视图；预警并入 KPI 缺货卡点击筛选；流水移商品详情
- 头部：库存管理 + 共 N 个 SKU·数据实时 + 列设置/导出（盘点/新增入库去掉，走专门菜单）
- KPI 4 卡走全店汇总接口：SKU总数/库存货值(Σqty×进价)/在库数量/缺货预警(可点筛选)
- 表格 12 列：加 库存(低库存染色)/成本价(进价)/单价(售价)；操作列只「查看详情」；状态圆点
- 仓库/备注默认隐藏；工具栏 搜索+状态筛选+重置
- 后端 GET /inventory/summary 全店汇总（守 shop_id）；前端 model/repository/provider 配套
- golden_harness：monospace 指向 Noto（消等宽数字黑块，全 golden 受益）；库存屏存量 grey 清零

后端编译/库存测试通过；前端 analyze 0 error，flutter test 242 通过；代码端颜色闸 0 违规。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TSKEiHsvauyxYUW2itzUXX

client/lib/models/inventory.dart

@@ -72,6 +72,29 @@ class Inventory {
       );
 }
 
+/// 全店库存 KPI 汇总（GET /inventory/summary，不随分页）。
+class InventorySummary {
+  final int skuCount;
+  final double stockValue;
+  final double inStockQty;
+  final int shortageCount;
+  final int warningCount;
+  const InventorySummary({
+    this.skuCount = 0,
+    this.stockValue = 0,
+    this.inStockQty = 0,
+    this.shortageCount = 0,
+    this.warningCount = 0,
+  });
+  factory InventorySummary.fromJson(Map<String, dynamic> j) => InventorySummary(
+        skuCount: (j['sku_count'] as num?)?.toInt() ?? 0,
+        stockValue: (j['stock_value'] as num?)?.toDouble() ?? 0,
+        inStockQty: (j['in_stock_qty'] as num?)?.toDouble() ?? 0,
+        shortageCount: (j['shortage_count'] as num?)?.toInt() ?? 0,
+        warningCount: (j['warning_count'] as num?)?.toInt() ?? 0,
+      );
+}
+
 class InventoryLog {
   final int warehouseId;
   final String? warehouseName;