fix(lint): 修复 golangci-lint 问题（gofmt + staticcheck）

backend/internal/service/account_usage_service.go

@@ -93,11 +93,11 @@ type UsageProgress struct {
 
 // UsageInfo 账号使用量信息
 type UsageInfo struct {
-	UpdatedAt      *time.Time     `json:"updated_at,omitempty"`       // 更新时间
-	FiveHour       *UsageProgress `json:"five_hour"`                  // 5小时窗口
-	SevenDay       *UsageProgress `json:"seven_day,omitempty"`        // 7天窗口
-	SevenDaySonnet *UsageProgress `json:"seven_day_sonnet,omitempty"` // 7天Sonnet窗口
-	GeminiProDaily *UsageProgress `json:"gemini_pro_daily,omitempty"` // Gemini Pro 日配额
+	UpdatedAt        *time.Time     `json:"updated_at,omitempty"`         // 更新时间
+	FiveHour         *UsageProgress `json:"five_hour"`                    // 5小时窗口
+	SevenDay         *UsageProgress `json:"seven_day,omitempty"`          // 7天窗口
+	SevenDaySonnet   *UsageProgress `json:"seven_day_sonnet,omitempty"`   // 7天Sonnet窗口
+	GeminiProDaily   *UsageProgress `json:"gemini_pro_daily,omitempty"`   // Gemini Pro 日配额
 	GeminiFlashDaily *UsageProgress `json:"gemini_flash_daily,omitempty"` // Gemini Flash 日配额
 }
 
@@ -124,10 +124,10 @@ type ClaudeUsageFetcher interface {
 
 // AccountUsageService 账号使用量查询服务
 type AccountUsageService struct {
-	accountRepo         AccountRepository
-	usageLogRepo        UsageLogRepository
-	usageFetcher        ClaudeUsageFetcher
-	geminiQuotaService  *GeminiQuotaService
+	accountRepo        AccountRepository
+	usageLogRepo       UsageLogRepository
+	usageFetcher       ClaudeUsageFetcher
+	geminiQuotaService *GeminiQuotaService
 }
 
 // NewAccountUsageService 创建AccountUsageService实例

backend/internal/service/gemini_messages_compat_service.go

@@ -1919,12 +1919,12 @@ func (s *GeminiMessagesCompatService) handleGeminiUpstreamError(ctx context.Cont
 		var ra time.Time
 		if isCodeAssist {
 			// Code Assist: fallback cooldown by tier
-				cooldown := geminiCooldownForTier(tierID)
-				if s.rateLimitService != nil {
-					cooldown = s.rateLimitService.GeminiCooldown(ctx, account)
-				}
+			cooldown := geminiCooldownForTier(tierID)
+			if s.rateLimitService != nil {
+				cooldown = s.rateLimitService.GeminiCooldown(ctx, account)
+			}
 			ra = time.Now().Add(cooldown)
-			log.Printf("[Gemini 429] Account %d (Code Assist, tier=%s, project=%s) rate limited, cooldown=%v", account.ID, tierID, projectID, ra.Sub(time.Now()).Truncate(time.Second))
+			log.Printf("[Gemini 429] Account %d (Code Assist, tier=%s, project=%s) rate limited, cooldown=%v", account.ID, tierID, projectID, time.Until(ra).Truncate(time.Second))
 		} else {
 			// API Key / AI Studio OAuth: PST 午夜
 			if ts := nextGeminiDailyResetUnix(); ts != nil {