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/main.tsx

@@ -1,19 +0,0 @@
-import React from "react";
-import ReactDOM from "react-dom/client";
-import App from "./App";
-import { ToastProvider } from "./shared/ui";
-import "./styles.css";
-
-const root = document.getElementById("root");
-
-if (!root) {
-  throw new Error("Root element not found");
-}
-
-ReactDOM.createRoot(root).render(
-  <React.StrictMode>
-    <ToastProvider>
-      <App />
-    </ToastProvider>
-  </React.StrictMode>,
-);