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/scheduler.py

@@ -0,0 +1,20 @@
+import asyncio
+from apscheduler.schedulers.asyncio import AsyncIOScheduler
+
+from .agents import AGENT_REGISTRY
+
+scheduler = AsyncIOScheduler(timezone="Asia/Seoul")
+
+async def _check_idle_breaks():
+    for agent in AGENT_REGISTRY.values():
+        await agent.check_idle_break()
+
+async def _run_stock_schedule():
+    agent = AGENT_REGISTRY.get("stock")
+    if agent:
+        await agent.on_schedule()
+
+def init_scheduler():
+    scheduler.add_job(_run_stock_schedule, "cron", hour=8, minute=0, id="stock_news")
+    scheduler.add_job(_check_idle_breaks, "interval", seconds=60, id="idle_check")
+    scheduler.start()