feat: add token auth, login page, skill toggle, and route restructure

- Add token-based authentication with auto-generated token stored in server/data/.token
- Add login page with URL token auto-fill support
- Add route guards requiring auth for all pages except login
- Restructure routes: / for login, /chat for conversations
- Add skill enable/disable toggle via config.yaml skills.disabled
- Unify logo to /logo.png across sidebar, login, messages, and empty state
- Hide sidebar on login page, prevent flash with router.isReady()
- Fix session export JSON parse error when CLI returns non-JSON output
- Display token in CLI on server start

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/i18n/locales/zh.ts

@@ -1,4 +1,15 @@
 export default {
+  // 登录
+  login: {
+    title: '登录',
+    description: '输入访问令牌以继续。令牌在服务端启动日志中查看。',
+    placeholder: '访问令牌',
+    submit: '登录',
+    tokenRequired: '请输入访问令牌',
+    invalidToken: '令牌无效',
+    connectionFailed: '无法连接到服务器',
+  },
+
   // 通用
   common: {
     loading: '加载中...',
@@ -133,6 +144,7 @@ export default {
     attachedFiles: '附件文件',
     loadFailed: '加载技能失败',
     fileLoadFailed: '加载文件失败',
+    toggleFailed: '切换技能状态失败',
   },
 
   // 记忆