feat(backend): 出入库编码搜索双路匹配+建单填快照；finance 趋势/日期区间；partner/product 拼音搜索

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JJ1g8XV1YhhmHRzhwWEW7o

backend/internal/handler/inventory_test.go

@@ -287,6 +287,79 @@ func TestInventoryHandler_List_DeletedProductFallsBackToSnapshot(t *testing.T) {
 	assert.Equal(t, float64(1), parseResponse(w)["total"].(float64))
 }
 
+// 商品编码独立筛选（?code=，库存屏第二个搜索框）
+func TestInventoryHandler_List_FilterByCode(t *testing.T) {
+	db := testutil.SetupTestDB()
+	shop := testutil.CreateTestShop(db, "INV_CODE")
+	user := testutil.CreateTestUser(db, shop.ID, "admin", "pass", "admin")
+	warehouse := testutil.CreateTestWarehouse(db, shop.ID, "Warehouse")
+	product1 := testutil.CreateTestProduct(db, shop.ID, "Beer1") // code=P-Beer1
+	product2 := testutil.CreateTestProduct(db, shop.ID, "Wine2") // code=P-Wine2
+	token := getAuthToken(user.ID, shop.ID, "admin")
+	r := setupProtectedRouter(db)
+
+	db.Create(&model.Inventory{ShopID: shop.ID, WarehouseID: &warehouse.ID, ProductID: &product1.ID, Quantity: 10})
+	db.Create(&model.Inventory{ShopID: shop.ID, WarehouseID: &warehouse.ID, ProductID: &product2.ID, Quantity: 20})
+
+	// 精确前缀命中一条
+	w := makeRequest(r, "GET", "/api/v1/inventory?code=P-Beer1", token, nil)
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Equal(t, float64(1), parseResponse(w)["total"].(float64))
+
+	// 模糊命中两条
+	w = makeRequest(r, "GET", "/api/v1/inventory?code=P-", token, nil)
+	assert.Equal(t, float64(2), parseResponse(w)["total"].(float64))
+
+	// 无命中
+	w = makeRequest(r, "GET", "/api/v1/inventory?code=NOPE", token, nil)
+	assert.Equal(t, float64(0), parseResponse(w)["total"].(float64))
+}
+
+// Summary 月初快照字段：月初数量 = 当前数量 − 本月净流水
+func TestInventoryHandler_Summary_LastMonth(t *testing.T) {
+	db := testutil.SetupTestDB()
+	shop := testutil.CreateTestShop(db, "INV_SUM")
+	user := testutil.CreateTestUser(db, shop.ID, "admin", "pass", "admin")
+	warehouse := testutil.CreateTestWarehouse(db, shop.ID, "Warehouse")
+	product1 := testutil.CreateTestProduct(db, shop.ID, "Old")
+	product2 := testutil.CreateTestProduct(db, shop.ID, "New")
+	token := getAuthToken(user.ID, shop.ID, "admin")
+	r := setupProtectedRouter(db)
+
+	now := time.Now()
+	monthStart := time.Date(now.Year(), now.Month(), 1, 0, 0, 0, 0, now.Location())
+	price1 := 100.0
+
+	// inv1：上月已存在（月初数量 = 30 − (25−5) = 10）
+	inv1 := model.Inventory{
+		ShopID: shop.ID, WarehouseID: &warehouse.ID, ProductID: &product1.ID,
+		Quantity: 30, UnitPrice: &price1,
+		CreatedAt: monthStart.AddDate(0, 0, -10),
+	}
+	require.NoError(t, db.Create(&inv1).Error)
+	// 本月流水：入 25、出 5 → 净 +20
+	db.Create(&model.InventoryLog{ShopID: shop.ID, WarehouseID: warehouse.ID, ProductID: product1.ID, Direction: "in", Quantity: 25})
+	db.Create(&model.InventoryLog{ShopID: shop.ID, WarehouseID: warehouse.ID, ProductID: product1.ID, Direction: "out", Quantity: 5})
+
+	// inv2：本月新入库，不计入月初快照
+	price2 := 10.0
+	db.Create(&model.Inventory{
+		ShopID: shop.ID, WarehouseID: &warehouse.ID, ProductID: &product2.ID,
+		Quantity: 5, UnitPrice: &price2,
+	})
+	db.Create(&model.InventoryLog{ShopID: shop.ID, WarehouseID: warehouse.ID, ProductID: product2.ID, Direction: "in", Quantity: 5})
+
+	w := makeRequest(r, "GET", "/api/v1/inventory/summary", token, nil)
+	assert.Equal(t, http.StatusOK, w.Code)
+	resp := parseResponse(w)
+	assert.Equal(t, float64(2), resp["sku_count"].(float64))
+	assert.Equal(t, float64(35), resp["in_stock_qty"].(float64))
+	assert.Equal(t, float64(30*100+5*10), resp["stock_value"].(float64))
+	assert.Equal(t, float64(1), resp["last_month_sku"].(float64))
+	assert.Equal(t, float64(10), resp["last_month_qty"].(float64))
+	assert.Equal(t, float64(10*100), resp["last_month_value"].(float64))
+}
+
 func TestInventoryHandler_AfterStockInApprove(t *testing.T) {
 	db := testutil.SetupTestDB()
 	shop := testutil.CreateTestShop(db, "INV008")