Bundle FastAPI backend into Next.js Docker container

The Next.js app was proxying /api/* to the old Flask/FastAPI server
at legal-ai.nautilus.marcusgroup.org. When that server went down,
the Next.js app's API calls failed with 503.

Now both services run in the same container:
- FastAPI (uvicorn) on :8000 — the API backend
- Next.js (node) on :3000 — proxies /api/* to localhost:8000

Changes:
- Dockerfile: multi-stage build with Python 3.12 + Node.js
- next.config.ts: default proxy target is now 127.0.0.1:8000
- start.sh: launches uvicorn in background + node in foreground
- pyproject.toml: add fastapi + uvicorn as explicit deps

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mcp-server/pyproject.toml

@@ -17,6 +17,8 @@ dependencies = [
     "rq>=1.16.0",
     "pillow>=10.0.0",
     "google-cloud-vision>=3.7.0",
+    "fastapi>=0.115.0",
+    "uvicorn[standard]>=0.30.0",
 ]
 
 [build-system]