feat(backend): 入库/出库列表 keyword 支持酒名模糊反查

- keyword 在单号/往来单位基础上，新增按酒名反查含该酒明细的单据
- 酒名匹配复用拼音基建：name(优先 product 回退快照) + name_pinyin + name_initials
- 子查询带 shop_id，多租户隔离不破
- 补 stock_in/stock_out List 按酒名+拼音命中的测试用例

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

backend/internal/handler/stock_in_test.go

@@ -451,6 +451,42 @@ func TestStockInHandler_List_FilterByKeyword(t *testing.T) {
 	assert.Equal(t, float64(2), parseResponse(w)["total"].(float64))
 }
 
+func TestStockInHandler_List_FilterByProductName(t *testing.T) {
+	db := testutil.SetupTestDB()
+	shop := testutil.CreateTestShop(db, "SI012")
+	user := testutil.CreateTestUser(db, shop.ID, "admin", "pass", "admin")
+	warehouse := testutil.CreateTestWarehouse(db, shop.ID, "Warehouse")
+	token := getAuthToken(user.ID, shop.ID, "admin")
+	r := setupProtectedRouter(db)
+
+	// 单据1：明细酒名「飞天茅台」（入库按 product_name 新建独立 product）
+	w := makeRequest(r, "POST", "/api/v1/stock-in/orders", token, map[string]interface{}{
+		"warehouse_id": warehouse.ID,
+		"order_date":   time.Now().Format(time.RFC3339),
+		"items":        []map[string]interface{}{{"product_name": "飞天茅台", "quantity": 5.0}},
+	})
+	require.Equal(t, http.StatusCreated, w.Code)
+
+	// 单据2：明细酒名「拉菲红酒」
+	w = makeRequest(r, "POST", "/api/v1/stock-in/orders", token, map[string]interface{}{
+		"warehouse_id": warehouse.ID,
+		"order_date":   time.Now().Format(time.RFC3339),
+		"items":        []map[string]interface{}{{"product_name": "拉菲红酒", "quantity": 3.0}},
+	})
+	require.Equal(t, http.StatusCreated, w.Code)
+
+	// 按酒名模糊反查 → 各命中 1 单
+	w = makeRequest(r, "GET", "/api/v1/stock-in/orders?keyword=茅台", token, nil)
+	assert.Equal(t, float64(1), parseResponse(w)["total"].(float64))
+
+	w = makeRequest(r, "GET", "/api/v1/stock-in/orders?keyword=红酒", token, nil)
+	assert.Equal(t, float64(1), parseResponse(w)["total"].(float64))
+
+	// 无关键词 → 两单都在
+	w = makeRequest(r, "GET", "/api/v1/stock-in/orders", token, nil)
+	assert.Equal(t, float64(2), parseResponse(w)["total"].(float64))
+}
+
 func TestStockInHandler_List_FilterByStatus(t *testing.T) {
 	db := testutil.SetupTestDB()
 	shop := testutil.CreateTestShop(db, "SI010")