refactor(api): introduce v1 response contract

backend/internal/logic/auth/handlers.go

@@ -24,12 +24,12 @@ func (h *Handler) login(c *gin.Context) {
 		Password string `json:"password"`
 	}
 	if err := c.ShouldBindJSON(&input); err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request"})
+		abortWithError(c, http.StatusBadRequest, "invalid_request", "请求参数无效")
 		return
 	}
 	token, err := h.service.Login(input.Email, input.Password)
 	if err != nil {
-		c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
+		abortWithError(c, http.StatusUnauthorized, "invalid_credentials", "邮箱或密码错误")
 		return
 	}
 	c.JSON(http.StatusOK, gin.H{"token": token})