feat(video-render): main.py + services/docker-compose entry (SP-7)

FastAPI lifespan에서 worker_loop 스폰. /health endpoint.
docker-compose: port 18712, NAS_BASE_URL default=18801 (video-lab),
4 provider env (OPENAI_API_KEY, GOOGLE_*, PIAPI_API_KEY, SEEDANCE_API_KEY),
GCP service account JSON read-only mount.
Plan-B-Video Phase 2 완료 — 박재오 머신에서 .env + GCP JSON 작성 + 빌드 대기.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/video-render/main.py

@@ -0,0 +1,36 @@
+"""video-render FastAPI entry — health + lifespan (worker loop spawn)."""
+from __future__ import annotations
+
+import asyncio
+import logging
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+
+import worker
+
+logging.basicConfig(level=logging.INFO, format="%(asctime)s %(name)s %(levelname)s %(message)s")
+logger = logging.getLogger(__name__)
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    worker_task = asyncio.create_task(worker.worker_loop())
+    logger.info("video-render lifespan 시작")
+    try:
+        yield
+    finally:
+        worker_task.cancel()
+        try:
+            await worker_task
+        except asyncio.CancelledError:
+            pass
+        logger.info("video-render lifespan 종료")
+
+
+app = FastAPI(lifespan=lifespan)
+
+
+@app.get("/health")
+def health():
+    return {"ok": True, "service": "video-render"}