feat: migrate and redesign dashboard to modern React

- Full rewrite of legacy vanilla JS UI into React SPA
- Implement modern design system using Tailwind CSS and shadcn/ui primitives
- Create typed API modules and hooks for voice, media, and moderation
- Add new features: separated Music and Screen Share panels, Image Grid
- Implement unified WebSocket hook for real-time state and PCM audio
- Improve visualizer with smooth CSS transitions and live state sync
- Add __dirname polyfill for ES module compatibility
- Ensure responsive layout for mobile and desktop

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/voice/VoicePanel.tsx

@@ -0,0 +1,41 @@
+import type { ActiveSpeaker, Channel, Guild, VoiceStatus } from "../../types/voice";
+import { AudioVisualizer } from "./AudioVisualizer";
+import { ActiveSpeakers } from "./ActiveSpeakers";
+import { VoiceControl } from "./VoiceControl";
+import { Card, CardContent, CardHeader, CardTitle } from "../ui/card";
+
+interface VoicePanelProps {
+  guilds: Guild[];
+  channels: Channel[];
+  selectedGuild: string;
+  selectedChannel: string;
+  status: VoiceStatus;
+  loading: boolean;
+  activeSpeakers: ActiveSpeaker[];
+  levels: number[];
+  isListening: boolean;
+  onGuildChange: (guildId: string) => void;
+  onChannelChange: (channelId: string) => void;
+  onJoin: () => void;
+  onDisconnect: () => void;
+  onListenToggle: () => void;
+}
+
+export function VoicePanel(props: VoicePanelProps) {
+  return (
+    <div className="grid gap-6">
+      <VoiceControl {...props} />
+      <div className="grid gap-6 xl:grid-cols-[1fr_360px]">
+        <Card>
+          <CardHeader>
+            <CardTitle>Live Audio Visualizer</CardTitle>
+          </CardHeader>
+          <CardContent>
+            <AudioVisualizer levels={props.levels} />
+          </CardContent>
+        </Card>
+        <ActiveSpeakers speakers={props.activeSpeakers} />
+      </div>
+    </div>
+  );
+}