fix: 修复 golangci-lint 检查错误

backend/internal/service/notification_email_service_test.go

@@ -665,7 +665,7 @@ func (s *notificationEmailTestSMTPServer) handleConn(conn net.Conn) {
 				if strings.TrimRight(dataLine, "\r\n") == "." {
 					break
 				}
-				message.WriteString(dataLine)
+				_, _ = message.WriteString(dataLine)
 			}
 			s.messageMu.Lock()
 			s.messageBodies = append(s.messageBodies, message.String())

backend/internal/service/ops_scheduled_report_service.go

@@ -537,13 +537,13 @@ func formatOpsReportInteger(value int64) string {
 
 	var builder strings.Builder
 	builder.Grow(len(raw) + (len(raw)-start-1)/3)
-	builder.WriteString(raw[:start])
+	_, _ = builder.WriteString(raw[:start])
 	digitLen := len(raw) - start
 	for offset := 0; offset < digitLen; offset++ {
 		if offset > 0 && (digitLen-offset)%3 == 0 {
-			builder.WriteByte(',')
+			_ = builder.WriteByte(',')
 		}
-		builder.WriteByte(raw[start+offset])
+		_ = builder.WriteByte(raw[start+offset])
 	}
 	return builder.String()
 }
@@ -625,11 +625,6 @@ func (s *OpsScheduledReportService) generateReportContent(ctx context.Context, r
 	}
 }
 
-func (s *OpsScheduledReportService) generateReportHTML(ctx context.Context, report *opsScheduledReport, now time.Time) (string, error) {
-	content, err := s.generateReportContent(ctx, report, now)
-	return content.html, err
-}
-
 func buildOpsSummaryEmailHTML(title string, start, end time.Time, overview *OpsDashboardOverview) string {
 	if overview == nil {
 		return fmt.Sprintf("<h2>%s</h2><p>No data.</p>", htmlEscape(title))