feat(chat): add local-first conversation workspace

site/account.html

@@ -17,7 +17,7 @@
       <a class="brand" href="/">xiteng.site / account</a>
       <div class="nav-links">
         <a id="account-admin-link" href="/admin" hidden>系统管理</a>
-        <a href="https://chat.xiteng.site">Chat</a>
+        <a href="/chat/">Chat</a>
         <a href="/">公开主页</a>
       </div>
     </nav>
@@ -80,7 +80,7 @@
         <div><p class="section-kicker">BUILT-IN + CUSTOM</p><h2>Provider Registry</h2></div>
         <button id="account-refresh" class="admin-action" type="button">刷新</button>
       </div>
-      <div class="admin-notice">只需填写 URL 与 API Key 即可先行探测；测试不会保存 Provider 或凭据。Backend Key 保存到 Key Vault；Frontend Key 必须跳转到 Chat 后保存在 <code>chat.xiteng.site</code> 的浏览器存储中。</div>
+      <div class="admin-notice">只需填写 URL 与 API Key 即可先行探测；测试不会保存 Provider 或凭据。Backend Key 保存到 Key Vault；Frontend Key 必须跳转到 Chat 后保存在 <code>xiteng.site/chat</code> 的浏览器存储中。</div>
       <form id="account-provider-form" class="admin-form provider-editor-form">
         <div class="provider-probe-fields">
           <label>Provider URL<input name="baseUrl" type="url" required placeholder="https://api.example.com/v1"></label>

site/account.js

@@ -485,7 +485,7 @@ function renderProvider(provider) {
   })));
   if (provider.connection.type === "frontend") {
     actions.append(actionButton(provider.auth.type === "none" ? "在 Chat 中配置端点" : "在 Chat 中配置本地 Key（需 CORS / Relay）", () => {
-      window.location.href = `https://chat.xiteng.site/?configure=${encodeURIComponent(provider.id)}`;
+      window.location.href = `/chat/?configure=${encodeURIComponent(provider.id)}`;
     }));
   }
   if (!provider.builtin) {
@@ -712,7 +712,7 @@ document.getElementById("account-provider-form").addEventListener("submit", asyn
         });
       }
     } else if (connectionType === "frontend") {
-      window.location.href = `https://chat.xiteng.site/?configure=${encodeURIComponent(providerId)}`;
+      window.location.href = `/chat/?configure=${encodeURIComponent(providerId)}`;
       return;
     }
     await loadVault();