feat(dashboard): add hide/show toggle for dashboard plugins in sidebar

- New config key: dashboard.hidden_plugins (list of plugin names)
- GET /api/dashboard/plugins now filters out hidden plugins from sidebar
- POST /api/dashboard/plugins/{name}/visibility toggles visibility
- Hub response includes user_hidden boolean per plugin row
- Eye/EyeOff toggle on plugin cards with dashboard manifests
- i18n: 'Show in sidebar' / 'Hide from sidebar' (en/zh)

web/src/i18n/zh.ts

@@ -291,6 +291,8 @@ export const zh: Translations = {
     authRequiredHint: "运行此命令以完成认证：",
     updateGit: "git pull",
     versionBadge: "版本",
+    showInSidebar: "在侧边栏显示",
+    hideFromSidebar: "从侧边栏隐藏",
   },
 
   skills: {