feat(agent-office): youtube_publisher 에이전트 + 30s 폴링

- YoutubePublisherAgent: 음악 파이프라인의 *_pending 상태를 폴링하여
  텔레그램 단일 채널로 단계별 검토 요청 발송, reply 수신 시 의도 분류
  후 music-lab에 feedback POST
- service_proxy: pipeline list/get/feedback/telegram-msg/lookup-by-msg
  헬퍼 5종 추가 (MUSIC_LAB_URL 사용)
- scheduler: 30초 interval로 poll_state_changes 실행
- telegram webhook: reply_to_message 가 파이프라인 메시지면
  youtube_publisher 로 라우팅 (슬래시 명령보다 우선)
- 테스트 4종 추가 (4 PASS)

agent-office/app/service_proxy.py

@@ -178,3 +178,46 @@ async def lotto_save_briefing(payload: dict) -> Dict[str, Any]:
     resp = await _client.post(f"{LOTTO_BACKEND_URL}/api/lotto/briefing", json=payload)
     resp.raise_for_status()
     return resp.json()
+
+
+# --- music-lab pipeline (YouTube publisher orchestration) ---
+
+async def list_active_pipelines() -> list[dict]:
+    async with httpx.AsyncClient(timeout=15) as client:
+        resp = await client.get(f"{MUSIC_LAB_URL}/api/music/pipeline?status=active")
+        resp.raise_for_status()
+        return resp.json().get("pipelines", [])
+
+
+async def get_pipeline(pid: int) -> dict:
+    async with httpx.AsyncClient(timeout=15) as client:
+        resp = await client.get(f"{MUSIC_LAB_URL}/api/music/pipeline/{pid}")
+        resp.raise_for_status()
+        return resp.json()
+
+
+async def post_pipeline_feedback(pid: int, step: str, intent: str,
+                                 feedback_text: Optional[str] = None) -> dict:
+    async with httpx.AsyncClient(timeout=15) as client:
+        resp = await client.post(
+            f"{MUSIC_LAB_URL}/api/music/pipeline/{pid}/feedback",
+            json={"step": step, "intent": intent, "feedback_text": feedback_text},
+        )
+        resp.raise_for_status()
+        return resp.json()
+
+
+async def save_pipeline_telegram_msg(pid: int, step: str, msg_id: int) -> None:
+    async with httpx.AsyncClient(timeout=10) as client:
+        await client.patch(
+            f"{MUSIC_LAB_URL}/api/music/pipeline/{pid}/telegram-msg",
+            json={"step": step, "message_id": msg_id},
+        )
+
+
+async def lookup_pipeline_by_msg(msg_id: int) -> Optional[dict]:
+    async with httpx.AsyncClient(timeout=10) as client:
+        resp = await client.get(f"{MUSIC_LAB_URL}/api/music/pipeline/lookup-by-msg/{msg_id}")
+        if resp.status_code == 200:
+            return resp.json()
+        return None