fix(backend): 架构质量改进批次二 (#32-37)

- #32 License 激活迁移到 license_devices 表：Activate/Verify/Deactivate 全部改用
  license_devices，新增 max_devices 校验和 GET /license/devices 端点；
  Activate 现在校验 shop_id 防跨租户激活
- #33 checkInventory 从 StockOutHandler 移到 StockService.CheckInventoryAvailability
- #34 新增 util/response.go 统一错误响应工具（RespondError/RespondSuccess/RespondCreated）
- #35 生产模式 CORS Origin='*' 启动时 Fatal
- #36 生产模式 License 私钥未配置启动时 Fatal
- #37 新增 util/page.go ValidatePageSize，应用到 partner/product/stock_in/stock_out handler

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/handler/license_test.go

@@ -25,16 +25,22 @@ func TestLicenseHandler_Activate_Success(t *testing.T) {
 		LicenseKey: "LHACT-BBBBB-CCCCC-DDDDD",
 		IsActive:   true,
 		ExpiresAt:  &expiry,
+		MaxDevices: 3,
 	}
 	require.NoError(t, db.Create(lic).Error)
 
 	w := makeRequest(r, "POST", "/api/v1/license/activate", token, map[string]interface{}{
 		"license_key": "LHACT-BBBBB-CCCCC-DDDDD",
 		"device_id":   "device-123",
+		"device_name": "Test Machine",
+		"platform":    "windows",
 	})
 	assert.Equal(t, http.StatusOK, w.Code)
-	data := parseResponse(w)["data"].(map[string]interface{})
-	assert.Equal(t, "device-123", data["device_id"])
+
+	// Verify device was recorded in license_devices
+	var dev model.LicenseDevice
+	require.NoError(t, db.Where("license_id = ? AND device_id = ?", lic.ID, "device-123").First(&dev).Error)
+	assert.Equal(t, "Test Machine", dev.DeviceName)
 }
 
 func TestLicenseHandler_Activate_MissingFields(t *testing.T) {
@@ -71,7 +77,7 @@ func TestLicenseHandler_Activate_NotFound(t *testing.T) {
 	assert.Equal(t, http.StatusBadRequest, w.Code)
 }
 
-func TestLicenseHandler_Activate_DeviceMismatch(t *testing.T) {
+func TestLicenseHandler_Activate_DeviceLimitExceeded(t *testing.T) {
 	db := testutil.SetupTestDB()
 	shop := testutil.CreateTestShop(db, "LH004")
 	user := testutil.CreateTestUser(db, shop.ID, "admin", "pass", "admin")
@@ -79,12 +85,13 @@ func TestLicenseHandler_Activate_DeviceMismatch(t *testing.T) {
 	r := setupProtectedRouter(db)
 
 	lic := &model.License{
-		ShopID:     shop.ID,
-		LicenseKey: "LHBND-BBBBB-CCCCC-DDDDD",
-		DeviceID:   "existing-device",
-		IsActive:   true,
+		ShopID: shop.ID, LicenseKey: "LHBND-BBBBB-CCCCC-DDDDD", IsActive: true, MaxDevices: 1,
 	}
 	require.NoError(t, db.Create(lic).Error)
+	// Fill the single allowed slot
+	require.NoError(t, db.Create(&model.LicenseDevice{
+		LicenseID: lic.ID, ShopID: shop.ID, DeviceID: "existing-device",
+	}).Error)
 
 	w := makeRequest(r, "POST", "/api/v1/license/activate", token, map[string]interface{}{
 		"license_key": "LHBND-BBBBB-CCCCC-DDDDD",
@@ -102,10 +109,7 @@ func TestLicenseHandler_Activate_Expired(t *testing.T) {
 
 	expiry := time.Now().Add(-24 * time.Hour)
 	lic := &model.License{
-		ShopID:     shop.ID,
-		LicenseKey: "LHEXP-BBBBB-CCCCC-DDDDD",
-		IsActive:   true,
-		ExpiresAt:  &expiry,
+		ShopID: shop.ID, LicenseKey: "LHEXP-BBBBB-CCCCC-DDDDD", IsActive: true, ExpiresAt: &expiry, MaxDevices: 3,
 	}
 	require.NoError(t, db.Create(lic).Error)
 
@@ -136,18 +140,15 @@ func TestLicenseHandler_Verify_Success(t *testing.T) {
 
 	expiry := time.Now().Add(30 * 24 * time.Hour)
 	lic := &model.License{
-		ShopID:     shop.ID,
-		LicenseKey: "LHVFY-BBBBB-CCCCC-DDDDD",
-		DeviceID:   "my-device",
-		IsActive:   true,
-		ExpiresAt:  &expiry,
+		ShopID: shop.ID, LicenseKey: "LHVFY-BBBBB-CCCCC-DDDDD", IsActive: true, ExpiresAt: &expiry,
 	}
 	require.NoError(t, db.Create(lic).Error)
+	require.NoError(t, db.Create(&model.LicenseDevice{
+		LicenseID: lic.ID, ShopID: shop.ID, DeviceID: "my-device",
+	}).Error)
 
 	w := makeRequest(r, "GET", "/api/v1/license/verify?device_id=my-device", token, nil)
 	assert.Equal(t, http.StatusOK, w.Code)
-	data := parseResponse(w)["data"].(map[string]interface{})
-	assert.Equal(t, "my-device", data["device_id"])
 }
 
 func TestLicenseHandler_Verify_MissingDeviceID(t *testing.T) {
@@ -181,13 +182,12 @@ func TestLicenseHandler_Verify_Expired(t *testing.T) {
 
 	expiry := time.Now().Add(-1 * time.Hour)
 	lic := &model.License{
-		ShopID:     shop.ID,
-		LicenseKey: "LHVEX-BBBBB-CCCCC-DDDDD",
-		DeviceID:   "expired-device",
-		IsActive:   true,
-		ExpiresAt:  &expiry,
+		ShopID: shop.ID, LicenseKey: "LHVEX-BBBBB-CCCCC-DDDDD", IsActive: true, ExpiresAt: &expiry,
 	}
 	require.NoError(t, db.Create(lic).Error)
+	require.NoError(t, db.Create(&model.LicenseDevice{
+		LicenseID: lic.ID, ShopID: shop.ID, DeviceID: "expired-device",
+	}).Error)
 
 	w := makeRequest(r, "GET", "/api/v1/license/verify?device_id=expired-device", token, nil)
 	assert.Equal(t, http.StatusForbidden, w.Code)
@@ -210,18 +210,22 @@ func TestLicenseHandler_Deactivate_Success(t *testing.T) {
 
 	expiry := time.Now().Add(30 * 24 * time.Hour)
 	lic := &model.License{
-		ShopID:     shop.ID,
-		LicenseKey: "LHDAC-BBBBB-CCCCC-DDDDD",
-		DeviceID:   "deactivate-device",
-		IsActive:   true,
-		ExpiresAt:  &expiry,
+		ShopID: shop.ID, LicenseKey: "LHDAC-BBBBB-CCCCC-DDDDD", IsActive: true, ExpiresAt: &expiry,
 	}
 	require.NoError(t, db.Create(lic).Error)
+	require.NoError(t, db.Create(&model.LicenseDevice{
+		LicenseID: lic.ID, ShopID: shop.ID, DeviceID: "deactivate-device",
+	}).Error)
 
 	w := makeRequest(r, "POST", "/api/v1/license/deactivate", token, map[string]interface{}{
 		"device_id": "deactivate-device",
 	})
 	assert.Equal(t, http.StatusOK, w.Code)
+
+	// Verify device was removed
+	var count int64
+	db.Model(&model.LicenseDevice{}).Where("shop_id = ? AND device_id = ?", shop.ID, "deactivate-device").Count(&count)
+	assert.Equal(t, int64(0), count)
 }
 
 func TestLicenseHandler_Deactivate_MissingDeviceID(t *testing.T) {