fix(lint): 修复 golangci-lint 检查问题

- 格式化代码（gofmt）
- 修复空指针检查（staticcheck）
- 删除未使用的函数（unused）

backend/internal/handler/ops_error_logger.go

@@ -1013,4 +1013,3 @@ func shouldSkipOpsErrorLog(ctx context.Context, ops *service.OpsService, message
 
 	return false
 }
-

backend/internal/repository/ops_repo.go

@@ -967,13 +967,15 @@ func buildOpsErrorLogsWhere(filter *service.OpsErrorLogFilter) (string, []any) {
 		args = append(args, phase)
 		clauses = append(clauses, "error_phase = $"+itoa(len(args)))
 	}
-	if owner := strings.TrimSpace(strings.ToLower(filter.Owner)); owner != "" {
-		args = append(args, owner)
-		clauses = append(clauses, "LOWER(COALESCE(error_owner,'')) = $"+itoa(len(args)))
-	}
-	if source := strings.TrimSpace(strings.ToLower(filter.Source)); source != "" {
-		args = append(args, source)
-		clauses = append(clauses, "LOWER(COALESCE(error_source,'')) = $"+itoa(len(args)))
+	if filter != nil {
+		if owner := strings.TrimSpace(strings.ToLower(filter.Owner)); owner != "" {
+			args = append(args, owner)
+			clauses = append(clauses, "LOWER(COALESCE(error_owner,'')) = $"+itoa(len(args)))
+		}
+		if source := strings.TrimSpace(strings.ToLower(filter.Source)); source != "" {
+			args = append(args, source)
+			clauses = append(clauses, "LOWER(COALESCE(error_source,'')) = $"+itoa(len(args)))
+		}
 	}
 	if resolvedFilter != nil {
 		args = append(args, *resolvedFilter)

backend/internal/service/ops_service.go

@@ -612,11 +612,3 @@ func sanitizeErrorBodyForStorage(raw string, maxBytes int) (sanitized string, tr
 	return raw, false
 }
 
-func extractString(v any, key string) string {
-	root, ok := v.(map[string]any)
-	if !ok {
-		return ""
-	}
-	s, _ := root[key].(string)
-	return strings.TrimSpace(s)
-}

backend/internal/service/ops_settings_models.go

@@ -78,13 +78,13 @@ type OpsAlertRuntimeSettings struct {
 
 // OpsAdvancedSettings stores advanced ops configuration (data retention, aggregation).
 type OpsAdvancedSettings struct {
-	DataRetention           OpsDataRetentionSettings `json:"data_retention"`
-	Aggregation             OpsAggregationSettings   `json:"aggregation"`
-	IgnoreCountTokensErrors bool                     `json:"ignore_count_tokens_errors"`
-	IgnoreContextCanceled   bool                     `json:"ignore_context_canceled"`
-	IgnoreNoAvailableAccounts bool                   `json:"ignore_no_available_accounts"`
-	AutoRefreshEnabled      bool                     `json:"auto_refresh_enabled"`
-	AutoRefreshIntervalSec  int                      `json:"auto_refresh_interval_seconds"`
+	DataRetention             OpsDataRetentionSettings `json:"data_retention"`
+	Aggregation               OpsAggregationSettings   `json:"aggregation"`
+	IgnoreCountTokensErrors   bool                     `json:"ignore_count_tokens_errors"`
+	IgnoreContextCanceled     bool                     `json:"ignore_context_canceled"`
+	IgnoreNoAvailableAccounts bool                     `json:"ignore_no_available_accounts"`
+	AutoRefreshEnabled        bool                     `json:"auto_refresh_enabled"`
+	AutoRefreshIntervalSec    int                      `json:"auto_refresh_interval_seconds"`
 }
 
 type OpsDataRetentionSettings struct {