fix(lint): 修复 golangci-lint 报错

- 修复 gofmt 格式问题
- 修复 staticcheck SA4031 nil check 问题（只在成功时设置 release 函数）
- 删除未使用的 sortAccountsByPriority 函数

backend/internal/handler/gateway_handler.go

@@ -192,9 +192,11 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 					log.Printf("Account wait queue full: account=%d", account.ID)
 					h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
 					return
-				}
-				accountWaitRelease = func() {
-					h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+				} else {
+					// Only set release function if increment succeeded
+					accountWaitRelease = func() {
+						h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+					}
 				}
 
 				accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
@@ -314,9 +316,11 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 				log.Printf("Account wait queue full: account=%d", account.ID)
 				h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
 				return
-			}
-			accountWaitRelease = func() {
-				h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+			} else {
+				// Only set release function if increment succeeded
+				accountWaitRelease = func() {
+					h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+				}
 			}
 
 			accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(

backend/internal/handler/gemini_v1beta_handler.go

@@ -233,9 +233,11 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 				log.Printf("Account wait queue full: account=%d", account.ID)
 				googleError(c, http.StatusTooManyRequests, "Too many pending requests, please retry later")
 				return
-			}
-			accountWaitRelease = func() {
-				geminiConcurrency.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+			} else {
+				// Only set release function if increment succeeded
+				accountWaitRelease = func() {
+					geminiConcurrency.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+				}
 			}
 
 			accountReleaseFunc, err = geminiConcurrency.AcquireAccountSlotWithWaitTimeout(

backend/internal/pkg/antigravity/claude_types.go

@@ -41,7 +41,7 @@ type ClaudeMetadata struct {
 // 1. 标准格式: { "name": "...", "description": "...", "input_schema": {...} }
 // 2. Custom 格式 (MCP): { "type": "custom", "name": "...", "custom": { "description": "...", "input_schema": {...} } }
 type ClaudeTool struct {
-	Type        string          `json:"type,omitempty"`         // "custom" 或空（标准格式）
+	Type        string          `json:"type,omitempty"` // "custom" 或空（标准格式）
 	Name        string          `json:"name"`
 	Description string          `json:"description,omitempty"`  // 标准格式使用
 	InputSchema map[string]any  `json:"input_schema,omitempty"` // 标准格式使用

backend/internal/service/gateway_service.go

@@ -681,12 +681,6 @@ func (s *GatewayService) tryAcquireAccountSlot(ctx context.Context, accountID in
 	return s.concurrencyService.AcquireAccountSlot(ctx, accountID, maxConcurrency)
 }
 
-func sortAccountsByPriority(accounts []*Account) {
-	sort.SliceStable(accounts, func(i, j int) bool {
-		return accounts[i].Priority < accounts[j].Priority
-	})
-}
-
 func sortAccountsByPriorityAndLastUsed(accounts []*Account, preferOAuth bool) {
 	sort.SliceStable(accounts, func(i, j int) bool {
 		a, b := accounts[i], accounts[j]