fix(phase2a): handleError 增强 + 代码格式化 + 测试报告归档

- auth/contact Controller handleError 增加 fallbackMsg 可变参数，未知错误可返回更有语义的降级提示
- import 排序、变量对齐等 gofmt 格式规范化
- 新增管理端测试报告和路由验证报告

Made-with: Cursor

backend/go-service/app/admin/service/user_manage_service.go

@@ -6,9 +6,9 @@ import (
 	"errors"
 	"math"
 
+	adminDAO "github.com/echochat/backend/app/admin/dao"
 	authDAO "github.com/echochat/backend/app/auth/dao"
 	"github.com/echochat/backend/app/auth/model"
-	adminDAO "github.com/echochat/backend/app/admin/dao"
 	"github.com/echochat/backend/app/constants"
 	"github.com/echochat/backend/app/dto"
 	"github.com/echochat/backend/pkg/logs"