feat: Add Plugin Configs landing page — collapse 9 sidebar items to 1

Replace individual plugin config sidebar entries with a single "Plugin Configs"
link that opens a card-based landing page. Cards show status (Active/Configured/
Not Configured), config count, and link to existing editor views. Search bar for
filtering. All existing plugin routes preserved for direct navigation.

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

frontend/src/router/index.ts

@@ -110,6 +110,11 @@ const panelRoutes: RouteRecordRaw[] = [
         name: 'files',
         component: () => import('@/views/admin/FileManagerView.vue'),
       },
+      {
+        path: 'plugin-configs',
+        name: 'plugin-configs',
+        component: () => import('@/views/admin/PluginConfigsView.vue'),
+      },
       {
         path: 'loot-builder',
         name: 'loot-builder',