feat(music-lab): wire redis client + internal_router + compose env (SP-6)

main.py에 redis.asyncio client 추가 + internal_router include.
docker-compose의 music-lab에 REDIS_URL/INTERNAL_API_KEY/MUSIC_RENDER_URL.
SUNO_API_KEY 라인 제거 (spec §9 — Windows로 이전).
Plan-B-Music Phase 1.

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

music-lab/app/main.py

@@ -36,9 +36,16 @@ from .suno_provider import (
     SUNO_API_KEY, SUNO_MODELS,
 )
 from .batch_generator import run_batch as _run_batch
+import redis.asyncio as aioredis
+from .internal_router import router as internal_router
 
 app = FastAPI()
 
+REDIS_URL = os.getenv("REDIS_URL", "redis://redis:6379")
+redis_client = aioredis.from_url(REDIS_URL, decode_responses=False)
+
+app.include_router(internal_router)
+
 _cors_origins = os.getenv("CORS_ALLOW_ORIGINS", "http://localhost:3007,http://localhost:8080").split(",")
 app.add_middleware(
     CORSMiddleware,