refactor: split monolith into 3 microservices (frontend, backend, discord-gateway)

- Extract services into services/{frontend,backend,discord-gateway}
- Create packages/shared/ for shared logger, errors, utils, types
- Setup Modular MVC pattern in backend (controller→service→repository)
- Setup event-driven architecture in discord-gateway with Redis pub/sub
- Move Docker files to infra/docker/ with per-service Dockerfiles
- Update docker-compose.yml to use Traefik-only routing (no port exposes)
- Update GitHub Actions deploy workflow for multi-service matrix build
- Fix all import paths and resolve type errors across all services
- All 3 services pass tsc --noEmit clean

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/frontend/src/shared/hooks/useAudioTransmit.ts

@@ -0,0 +1,63 @@
+// ─── Audio transmit hook — captures mic, encodes to PCM, sends via WebSocket ──
+import { useCallback, useRef, useState } from "react";
+
+const SAMPLE_RATE = 24000;
+
+export function useAudioTransmit(socketRef: {
+  readonly current: WebSocket | null;
+}) {
+  const [isStreaming, setIsStreaming] = useState(false);
+  const streamRef = useRef<MediaStream | null>(null);
+  const audioContextRef = useRef<AudioContext | null>(null);
+  const processorRef = useRef<ScriptProcessorNode | null>(null);
+
+  const stop = useCallback(() => {
+    setIsStreaming(false);
+    if (processorRef.current) {
+      processorRef.current.disconnect();
+      processorRef.current = null;
+    }
+    if (audioContextRef.current) {
+      audioContextRef.current.close();
+      audioContextRef.current = null;
+    }
+    if (streamRef.current) {
+      for (const track of streamRef.current.getTracks()) track.stop();
+      streamRef.current = null;
+    }
+  }, []);
+
+  const start = useCallback(async () => {
+    const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
+    streamRef.current = stream;
+    setIsStreaming(true);
+    const AudioContextCtor =
+      window.AudioContext ||
+      (window as unknown as { webkitAudioContext: typeof AudioContext })
+        .webkitAudioContext;
+    const audioContext = new AudioContextCtor({ sampleRate: SAMPLE_RATE });
+    audioContextRef.current = audioContext;
+    const source = audioContext.createMediaStreamSource(stream);
+    const processor = audioContext.createScriptProcessor(4096, 1, 1);
+    processorRef.current = processor;
+    source.connect(processor);
+    processor.connect(audioContext.destination);
+    processor.onaudioprocess = (event) => {
+      if (!socketRef.current || socketRef.current.readyState !== WebSocket.OPEN)
+        return;
+      const inputData = event.inputBuffer.getChannelData(0);
+      const pcmData = new Int16Array(inputData.length);
+      for (let i = 0; i < inputData.length; i++)
+        pcmData[i] = Math.max(-1, Math.min(1, inputData[i])) * 32767;
+      // BUG 2 FIX: slice() to create independent copy of the ArrayBuffer
+      socketRef.current.send(pcmData.buffer.slice(0));
+    };
+  }, [socketRef]);
+
+  const toggle = useCallback(async () => {
+    if (isStreaming) stop();
+    else await start();
+  }, [isStreaming, start, stop]);
+
+  return { isStreaming, toggle, stop, start };
+}