fix: Antigravity 账户刷新 token 500 错误

AccountHandler.Refresh 方法缺少对 Antigravity 平台的处理分支，
导致刷新时错误地走进 Claude 刷新逻辑。

backend/cmd/server/wire_gen.go

@@ -105,7 +105,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	concurrencyCache := repository.ProvideConcurrencyCache(redisClient, configConfig)
 	concurrencyService := service.ProvideConcurrencyService(concurrencyCache, accountRepository, configConfig)
 	crsSyncService := service.NewCRSSyncService(accountRepository, proxyRepository, oAuthService, openAIOAuthService, geminiOAuthService)
-	accountHandler := admin.NewAccountHandler(adminService, oAuthService, openAIOAuthService, geminiOAuthService, rateLimitService, accountUsageService, accountTestService, concurrencyService, crsSyncService)
+	accountHandler := admin.NewAccountHandler(adminService, oAuthService, openAIOAuthService, geminiOAuthService, antigravityOAuthService, rateLimitService, accountUsageService, accountTestService, concurrencyService, crsSyncService)
 	oAuthHandler := admin.NewOAuthHandler(oAuthService)
 	openAIOAuthHandler := admin.NewOpenAIOAuthHandler(openAIOAuthService, adminService)
 	geminiOAuthHandler := admin.NewGeminiOAuthHandler(geminiOAuthService)

backend/internal/handler/admin/account_handler.go

@@ -38,6 +38,7 @@ type AccountHandler struct {
 	oauthService            *service.OAuthService
 	openaiOAuthService      *service.OpenAIOAuthService
 	geminiOAuthService      *service.GeminiOAuthService
+	antigravityOAuthService *service.AntigravityOAuthService
 	rateLimitService        *service.RateLimitService
 	accountUsageService     *service.AccountUsageService
 	accountTestService      *service.AccountTestService
@@ -51,6 +52,7 @@ func NewAccountHandler(
 	oauthService *service.OAuthService,
 	openaiOAuthService *service.OpenAIOAuthService,
 	geminiOAuthService *service.GeminiOAuthService,
+	antigravityOAuthService *service.AntigravityOAuthService,
 	rateLimitService *service.RateLimitService,
 	accountUsageService *service.AccountUsageService,
 	accountTestService *service.AccountTestService,
@@ -62,6 +64,7 @@ func NewAccountHandler(
 		oauthService:            oauthService,
 		openaiOAuthService:      openaiOAuthService,
 		geminiOAuthService:      geminiOAuthService,
+		antigravityOAuthService: antigravityOAuthService,
 		rateLimitService:        rateLimitService,
 		accountUsageService:     accountUsageService,
 		accountTestService:      accountTestService,
@@ -415,6 +418,19 @@ func (h *AccountHandler) Refresh(c *gin.Context) {
 				newCredentials[k] = v
 			}
 		}
+	} else if account.Platform == service.PlatformAntigravity {
+		tokenInfo, err := h.antigravityOAuthService.RefreshAccountToken(c.Request.Context(), account)
+		if err != nil {
+			response.ErrorFrom(c, err)
+			return
+		}
+
+		newCredentials = h.antigravityOAuthService.BuildAccountCredentials(tokenInfo)
+		for k, v := range account.Credentials {
+			if _, exists := newCredentials[k]; !exists {
+				newCredentials[k] = v
+			}
+		}
 	} else {
 		// Use Anthropic/Claude OAuth service to refresh token
 		tokenInfo, err := h.oauthService.RefreshAccountToken(c.Request.Context(), account)