feat: 新增「关于」和「扩展工具」页面

- 关于页面：版本信息、相关项目链接、快捷链接、开源协议
- 扩展页面：cftunnel 隧道状态/路由/启停/日志 + ClawApp 状态/快捷访问
- Rust 后端：新增 extensions.rs（4 个命令：状态/操作/日志/ClawApp 检测）
- 侧边栏新增「扩展」和「关于」导航项，总计 8 个页面

src/components/sidebar.js

@@ -25,6 +25,18 @@ const NAV_ITEMS = [
     items: [
       { route: '/memory', label: '记忆文件', icon: 'memory' },
     ]
+  },
+  {
+    section: '扩展',
+    items: [
+      { route: '/extensions', label: '扩展工具', icon: 'extensions' },
+    ]
+  },
+  {
+    section: '',
+    items: [
+      { route: '/about', label: '关于', icon: 'about' },
+    ]
   }
 ]
 
@@ -35,6 +47,8 @@ const ICONS = {
   models: '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M21 16V8a2 2 0 00-1-1.73l-7-4a2 2 0 00-2 0l-7 4A2 2 0 003 8v8a2 2 0 001 1.73l7 4a2 2 0 002 0l7-4A2 2 0 0021 16z"/><path d="M3.27 6.96L12 12.01l8.73-5.05M12 22.08V12"/></svg>',
   gateway: '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><rect x="2" y="2" width="20" height="8" rx="2"/><rect x="2" y="14" width="20" height="8" rx="2"/><line x1="6" y1="6" x2="6.01" y2="6"/><line x1="6" y1="18" x2="6.01" y2="18"/></svg>',
   memory: '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M2 3h6a4 4 0 014 4v14a3 3 0 00-3-3H2z"/><path d="M22 3h-6a4 4 0 00-4 4v14a3 3 0 013-3h7z"/></svg>',
+  extensions: '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M12 2l3.09 6.26L22 9.27l-5 4.87 1.18 6.88L12 17.77l-6.18 3.25L7 14.14 2 9.27l6.91-1.01L12 2z"/></svg>',
+  about: '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="12" cy="12" r="10"/><line x1="12" y1="16" x2="12" y2="12"/><line x1="12" y1="8" x2="12.01" y2="8"/></svg>',
 }
 
 let _delegated = false