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/models.py

@@ -0,0 +1,35 @@
+from pydantic import BaseModel
+from typing import Optional
+
+
+class CommandRequest(BaseModel):
+    agent: str
+    action: str
+    params: Optional[dict] = None
+
+
+class ApprovalRequest(BaseModel):
+    agent: str
+    task_id: str
+    approved: bool
+    feedback: Optional[str] = None
+
+
+class AgentConfigUpdate(BaseModel):
+    enabled: Optional[bool] = None
+    schedule_config: Optional[dict] = None
+    custom_config: Optional[dict] = None
+
+
+class PriceAlertConfig(BaseModel):
+    symbol: str
+    name: str
+    target_price: float
+    direction: str  # "above" or "below"
+
+
+class ComposeCommand(BaseModel):
+    prompt: str
+    style: Optional[str] = None
+    model: Optional[str] = "V4"
+    instrumental: Optional[bool] = False