施工(HEL-226): 实现登录门户与本机免密切换账号

用设备 Cookie 和授权表记住本机已验证账号，登录页按确认样图做成门户，不再把密码写进浏览器。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

frontend/shared/session.js

@@ -53,12 +53,10 @@ async function applyAuthenticatedSession(session) {
 function showAuthGate(message = "") {
   state.user = null;
   state.csrfToken = "";
-  const gate = document.querySelector("#authGate");
-  gate.hidden = false;
-  const errorElement = document.querySelector("#authError");
-  errorElement.textContent = message;
-  errorElement.hidden = !message;
-  document.querySelector("#authUsername").focus();
+  const params = new URLSearchParams();
+  if (message) params.set("notice", message);
+  const query = params.toString();
+  window.location.replace("/login/" + (query ? `?${query}` : ""));
 }
 
 async function logoutAccount() {
@@ -197,16 +195,8 @@ async function changeAccountPassword(event) {
 }
 
 async function switchAccount() {
-  const button = document.querySelector("#switchAccountMenuButton");
-  button.disabled = true;
   toggleAccountDropdown(false);
-  try {
-    await apiRequest("/api/auth/logout", "POST", {});
-    window.location.reload();
-  } catch (error) {
-    showToast(error.message || "切换账号失败");
-    button.disabled = false;
-  }
+  window.location.assign("/login/");
 }