feat: migrate frontend to Astro + expand AI moderation + backend admin/runtime config

Frontend:
- migrate from Vite to Astro (astro.config.mjs, pages/, layouts/)
- add admin panel, settings page, command palette, error boundary
- refactor App.tsx, MascotChatbot, Sidebar, Header, DashboardLayout
- update API client, WebSocket, auth, dashboard features

Backend:
- add admin module and config routes
- refactor middlewares, Redis connection, WebSocket server/bridge
- add runtime config loader

Discord Gateway:
- refactor AI moderation: circuit breaker, concurrency limiter, fallback processor
- add media analysis client, Seaxng search, user profile learner
- add new drizzle migration

Shared:
- extend database schema, add new config fields

services/frontend/src/features/dashboard/index.tsx

@@ -1,4 +1,6 @@
+import { Settings } from "lucide-react";
 import { useState } from "react";
+import { AdminPanel } from "../../features/admin/AdminPanel";
 import { Tabs, TabsContent, TabsList, TabsTrigger } from "../../shared/ui";
 import { ChannelProfileDetail } from "./components/ChannelProfileDetail";
 import { ChannelSummaryList } from "./components/ChannelSummaryList";
@@ -87,6 +89,10 @@ export function DashboardPanel() {
         <TabsTrigger value="stats">Stats</TabsTrigger>
         <TabsTrigger value="users">Users</TabsTrigger>
         <TabsTrigger value="channels">Channels</TabsTrigger>
+        <TabsTrigger value="admin" className="flex items-center gap-1.5">
+          <Settings className="h-3.5 w-3.5" />
+          Admin
+        </TabsTrigger>
       </TabsList>
 
       <TabsContent value="stats">
@@ -120,6 +126,10 @@ export function DashboardPanel() {
           onSelectChannel={setSelectedChannelId}
         />
       </TabsContent>
+
+      <TabsContent value="admin">
+        <AdminPanel />
+      </TabsContent>
     </Tabs>
   );
 }