feat: WebUI 框架设置页面 + API Key 管理 UI

新增:
- static/web_panel/pages/settings.html — API Key CRUD 界面
- 侧边栏 '框架设置' 导航项 (齿轮图标)
- BUILTIN_PAGES 增加 'settings'
- UI 功能: 创建对话框(名称/权限/过期), 列表表格, 一键删除

权限模板:
- readonly — framework.status.read + plugin.info.read
- monitor — + framework.event.subscribe
- full — admin (全部)

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

static/web_panel/js/app.js

@@ -26,7 +26,7 @@ window.toggleTheme = function(){
 // Built-in pages map to ./static/pages/{name}.html
 // Plugin pages load from /plugin/{name}
 
-var BUILTIN_PAGES = ['dashboard','logs','console','plugins','projects','proxy','files'];
+var BUILTIN_PAGES = ['dashboard','logs','console','plugins','projects','proxy','files','settings'];
 var _pluginPagesCache = null; // {plugin_name: {path, title, icon}}
 
 function currentRoute() {