fix: Antigravity 刷新 token 时检测 project_id 缺失

- 刷新 token 后调用 LoadCodeAssist 获取 project_id
- 如果获取失败，保留原有 project_id，标记账户为 error
- token 仍会正常更新，不影响凭证刷新
- 错误信息：账户缺少project id，可能无法使用Antigravity

backend/internal/handler/admin/account_handler.go

@@ -450,6 +450,28 @@ func (h *AccountHandler) Refresh(c *gin.Context) {
 				newCredentials[k] = v
 			}
 		}
+
+		// 如果 project_id 获取失败，先更新凭证，再标记账户为 error
+		if tokenInfo.ProjectIDMissing {
+			// 先更新凭证
+			_, updateErr := h.adminService.UpdateAccount(c.Request.Context(), accountID, &service.UpdateAccountInput{
+				Credentials: newCredentials,
+			})
+			if updateErr != nil {
+				response.InternalError(c, "Failed to update credentials: "+updateErr.Error())
+				return
+			}
+			// 标记账户为 error
+			if setErr := h.adminService.SetAccountError(c.Request.Context(), accountID, "账户缺少project id，可能无法使用Antigravity"); setErr != nil {
+				response.InternalError(c, "Failed to set account error: "+setErr.Error())
+				return
+			}
+			response.Success(c, gin.H{
+				"message": "Token refreshed but project_id is missing, account marked as error",
+				"warning": "missing_project_id",
+			})
+			return
+		}
 	} else {
 		// Use Anthropic/Claude OAuth service to refresh token
 		tokenInfo, err := h.oauthService.RefreshAccountToken(c.Request.Context(), account)