feat: Agent Office — AI 에이전트 가상 오피스 (#2)

## Summary
- 2D 픽셀아트 가상 오피스에서 AI 에이전트(Stock, Music)가 실제 작업 수행
- FastAPI + WebSocket 실시간 상태 동기화 + 텔레그램 봇 양방향 알림/승인
- BaseAgent FSM (idle/working/waiting/reporting/break), 서비스 프록시 패턴
- Docker Compose 서비스 (port 18900) + Nginx WebSocket 프록시

## Changes (13 commits)
- Backend scaffold: config, db, models, Dockerfile
- WebSocket manager + Service proxy
- BaseAgent FSM + StockAgent + MusicAgent
- Telegram bot + Scheduler
- FastAPI main (REST + WS endpoints)
- Infrastructure: docker-compose + nginx
- Code review fixes: HTTPException, async polling, input validation

Reviewed-on: #2

agent-office/app/agents/music.py

@@ -0,0 +1,124 @@
+import asyncio
+from .base import BaseAgent
+from ..db import create_task, update_task_status, approve_task, reject_task, add_log
+from .. import service_proxy
+from .. import telegram_bot
+
+class MusicAgent(BaseAgent):
+    agent_id = "music"
+    display_name = "음악 프로듀서"
+
+    async def on_schedule(self) -> None:
+        pass
+
+    async def on_command(self, command: str, params: dict) -> dict:
+        if command == "compose":
+            prompt = params.get("prompt", "")
+            style = params.get("style", "")
+            model = params.get("model", "V4")
+            instrumental = params.get("instrumental", False)
+
+            if not prompt:
+                return {"ok": False, "message": "프롬프트를 입력해주세요"}
+
+            task_id = create_task(self.agent_id, "compose", {
+                "prompt": prompt, "style": style,
+                "model": model, "instrumental": instrumental,
+            }, requires_approval=True)
+
+            await self.transition("waiting", "프롬프트 승인 대기", task_id)
+
+            detail = f"프롬프트: {prompt}"
+            if style:
+                detail += f"\n스타일: {style}"
+            detail += f"\n모델: {model}"
+
+            await telegram_bot.send_approval_request(
+                self.agent_id, task_id,
+                "🎵 [음악 에이전트] 작곡 요청", detail,
+            )
+
+            return {"ok": True, "task_id": task_id, "message": "승인 대기 중"}
+
+        if command == "credits":
+            credits = await service_proxy.get_music_credits()
+            return {"ok": True, "credits": credits}
+
+        return {"ok": False, "message": f"Unknown command: {command}"}
+
+    async def on_approval(self, task_id: str, approved: bool, feedback: str = "") -> None:
+        if not approved:
+            reject_task(task_id)
+            await self.transition("idle", "작곡 거절됨")
+            await telegram_bot.send_task_result(
+                self.agent_id, "🎵 [음악 에이전트] 작곡 취소",
+                "사용자가 거절했습니다.",
+            )
+            return
+
+        from ..db import get_task
+        task = get_task(task_id)
+        if not task:
+            return
+
+        approve_task(task_id, via="telegram")
+        await self.transition("working", "작곡 중...", task_id)
+        asyncio.create_task(self._poll_composition(task_id, task))
+
+    async def _poll_composition(self, task_id: str, task: dict) -> None:
+        try:
+            input_data = task["input_data"]
+            payload = {
+                "provider": "suno",
+                "model": input_data.get("model", "V4"),
+                "prompt": input_data.get("prompt", ""),
+                "style": input_data.get("style", ""),
+                "instrumental": input_data.get("instrumental", False),
+                "custom_mode": True,
+            }
+
+            result = await service_proxy.generate_music(payload)
+            music_task_id = result.get("task_id")
+
+            if not music_task_id:
+                raise Exception("music-lab did not return task_id")
+
+            for _ in range(60):
+                await asyncio.sleep(5)
+                status = await service_proxy.get_music_status(music_task_id)
+                state = status.get("status", "")
+
+                if state == "succeeded":
+                    tracks = status.get("tracks", [])
+                    update_task_status(task_id, "succeeded", {
+                        "music_task_id": music_task_id,
+                        "tracks": tracks,
+                    })
+                    await self.transition("reporting", "작곡 완료!")
+
+                    track_info = ""
+                    for t in tracks:
+                        title = t.get("title", "Untitled")
+                        url = t.get("audio_url", "")
+                        track_info += f"🎶 {title}\n{url}\n"
+
+                    await telegram_bot.send_task_result(
+                        self.agent_id, "🎵 [음악 에이전트] 작곡 완료",
+                        track_info or "트랙 생성 완료",
+                    )
+                    await self.transition("idle", "작곡 완료")
+                    return
+
+                if state == "failed":
+                    raise Exception(status.get("message", "Generation failed"))
+
+            raise Exception("Timeout: 5분 초과")
+
+        except Exception as e:
+            add_log(self.agent_id, f"Compose failed: {e}", "error", task_id)
+            update_task_status(task_id, "failed", {"error": str(e)})
+            await self.transition("idle", f"오류: {e}")
+            await telegram_bot.send_task_result(
+                self.agent_id, "🎵 [음악 에이전트] 작곡 실패",
+                f"오류: {e}",
+            )