feat: Add Comfy Agent service for NODE3 image/video generation

- Create comfy-agent service with FastAPI + NATS integration
- ComfyUI client with HTTP/WebSocket support
- REST API: /generate/image, /generate/video, /status, /result
- NATS subjects: agent.invoke.comfy, comfy.request.*
- Async job queue with progress tracking
- Docker compose configuration for NODE3
- Update PROJECT-MASTER-INDEX.md with NODE2/NODE3 docs

Co-Authored-By: Warp <agent@warp.dev>

services/comfy-agent/app/storage.py

@@ -0,0 +1,16 @@
+# services/comfy-agent/app/storage.py
+import os
+from pathlib import Path
+from .config import settings
+
+def ensure_storage() -> None:
+    Path(settings.STORAGE_PATH).mkdir(parents=True, exist_ok=True)
+
+def make_job_dir(job_id: str) -> str:
+    ensure_storage()
+    d = os.path.join(settings.STORAGE_PATH, job_id)
+    Path(d).mkdir(parents=True, exist_ok=True)
+    return d
+
+def public_url(job_id: str, filename: str) -> str:
+    return f"{settings.PUBLIC_BASE_URL}/{job_id}/{filename}"