feat: migrate frontend to Astro SSG with design system

- Replace monolithic React SPA (App.tsx) with 7 Astro pages (+ routing)
- Implement full design system from design/ (OKLCH tokens, Tailwind 4 @theme)
- Add 12 Astro components (Button, Badge, Card, Sidebar, Header, states)
- Add 11 React islands (AuthGuard, MessageFeed, VoiceControls, AudioVisualizer, etc.)
- Add 3 Zustand stores (UI, voice, message state)
- Add CSS architecture: dark/light themes, glassmorphism, fluid typography, animations
- Add 404, login, settings, recordings pages
- Remove 40+ legacy React SPA files
- Add Particles background and MascotChat deferred islands
- Wire WebSocket bridge for real-time messages and voice events

Build: 7 pages in ~900ms
Typecheck: clean (0 errors)
Lint: clean (0 errors)

services/frontend/src/App.client.tsx

@@ -1,18 +0,0 @@
-// ─── App.client.tsx — Astro React island entry point ────────────────────────
-// DILOAD OLEH Astro client:only="react"
-// Menyediakan <div id="root"> dan mount App dengan provider yang diperlukan
-// ─────────────────────────────────────────────────────────────────────────────
-
-import React from "react";
-import App from "./App";
-import { ToastProvider } from "./shared/ui";
-
-export default function AppClient() {
-  return (
-    <React.StrictMode>
-      <ToastProvider>
-        <App />
-      </ToastProvider>
-    </React.StrictMode>
-  );
-}