Integrate Qiniu upload service and update configuration

- Added Qiniu configuration options to .env.example and config.go for file uploads.
- Refactored main.go to include new Qiniu service and upload handler.
- Updated route registration to accommodate the new upload handler.
- Enhanced documentation to include references for Qiniu upload functionality.
- Removed legacy authentication handler and services to streamline the codebase.

internal/common/auth/service/mini_program_service.go

@@ -0,0 +1,28 @@
+package service
+
+import (
+	"context"
+
+	"wx_service/internal/model"
+
+	"gorm.io/gorm"
+)
+
+type MiniProgramService struct {
+	// service 层负责“业务能力”，通常会依赖数据库/第三方客户端等基础设施。
+	// 这里通过结构体字段持有 db（依赖注入），而不是在方法里自己创建连接。
+	db *gorm.DB
+}
+
+func NewMiniProgramService(db *gorm.DB) *MiniProgramService {
+	return &MiniProgramService{db: db}
+}
+
+func (s *MiniProgramService) GetByID(ctx context.Context, id uint) (*model.MiniProgram, error) {
+	// WithContext(ctx) 能把请求的超时/取消信号传递给数据库层，避免慢请求一直挂着。
+	var mp model.MiniProgram
+	if err := s.db.WithContext(ctx).Where("id = ?", id).First(&mp).Error; err != nil {
+		return nil, err
+	}
+	return &mp, nil
+}