feat(client): 新建出入库单默认填充默认仓库（两端，原型同步）

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

client/lib/screens/stock_in/stock_in_form_screen.dart

@@ -75,9 +75,26 @@ class _StockInFormScreenState extends ConsumerState<StockInFormScreen> {
     } else {
       _items.add(_ItemRow());
       _initDefaults();
+      _initWarehouseDefault();
     }
   }
 
+  /// 新建单默认填充默认仓库（2026-07-14）：仓库列表加载完成后，
+  /// `isDefault` 的仓 优先；无默认时仅剩 1 个仓才取它；否则保持 null。
+  /// 编辑模式不受影响（`_loadEditOrder` 已从单据自身仓库回填）。
+  Future<void> _initWarehouseDefault() async {
+    try {
+      final warehouses = await ref.read(warehouseListProvider.future);
+      if (!mounted || _warehouseId != null) return;
+      final defaultWh = warehouses.where((w) => w.isDefault).firstOrNull;
+      final picked = defaultWh?.id ??
+          (warehouses.length == 1 ? warehouses.first.id : null);
+      if (picked != null) {
+        setState(() => _warehouseId = picked);
+      }
+    } catch (_) {}
+  }
+
   Future<void> _initDefaults() async {
     try {
       final shop = await ref.read(shopInfoProvider.future);

client/lib/screens/stock_out/stock_out_form_screen.dart

@@ -173,8 +173,29 @@ class _StockOutFormScreenState extends ConsumerState<StockOutFormScreen> {
   @override
   void initState() {
     super.initState();
-    if (_isEdit) _loadEditOrder();
-    // 新单起始为空，用户通过「从库存选择」添加明细
+    if (_isEdit) {
+      _loadEditOrder();
+    } else {
+      // 新单起始为空，用户通过「从库存选择」添加明细
+      _initWarehouseDefault();
+    }
+  }
+
+  /// 新建单默认填充默认仓库（2026-07-14）：仓库列表加载完成后，
+  /// `isDefault` 的仓 优先；无默认时仅剩 1 个仓才取它；否则保持 null。
+  /// 编辑模式不受影响（`_loadEditOrder` 已从单据自身仓库回填）。
+  Future<void> _initWarehouseDefault() async {
+    try {
+      final warehouses = await ref.read(warehouseListProvider.future);
+      if (!mounted || _warehouseId != null) return;
+      final defaultWh = warehouses.where((w) => w.isDefault).firstOrNull;
+      final picked = defaultWh?.id ??
+          (warehouses.length == 1 ? warehouses.first.id : null);
+      if (picked != null) {
+        setState(() => _warehouseId = picked);
+        await _loadInventory(picked);
+      }
+    } catch (_) {}
   }
 
   Future<void> _loadEditOrder() async {