refactor: 移除全局单例、修复分层违规、统一错误与响应

internal/handler/auth_handler.go

@@ -4,7 +4,6 @@ import (
 	"carrotskin/internal/container"
 	"carrotskin/internal/service"
 	"carrotskin/internal/types"
-	"carrotskin/pkg/email"
 
 	"github.com/gin-gonic/gin"
 	"go.uber.org/zap"
@@ -177,8 +176,3 @@ func (h *AuthHandler) ResetPassword(c *gin.Context) {
 
 	RespondSuccess(c, gin.H{"message": "密码重置成功"})
 }
-
-// getEmailService 获取邮件服务（暂时使用全局方式，后续可改为依赖注入）
-func (h *AuthHandler) getEmailService() (*email.Service, error) {
-	return email.GetService()
-}