fix(backend): handle defer Close() errors in crs_sync_service

修复 golangci-lint 错误检查问题
- 使用匿名函数包装 defer Close() 并忽略错误
- 符合 Go 最佳实践

backend/internal/service/crs_sync_service.go

@@ -783,7 +783,7 @@ func crsLogin(ctx context.Context, client *http.Client, baseURL, username, passw
 	if err != nil {
 		return "", err
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 
 	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
@@ -818,7 +818,7 @@ func crsExportAccounts(ctx context.Context, client *http.Client, baseURL, adminT
 	if err != nil {
 		return nil, err
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 
 	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 5<<20))
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {