feat: implement MC domain filter proxy, API, dashboard

- proxy: asyncio TCP proxy with handshake parser, domain whitelist,
  transparent backend tunneling, SQLite logging, mtime hot reload
- api: FastAPI routes for config/domains/logs/status + restart trigger
- frontend: React + Vite NPM-style dashboard (dashboard/domains/logs/settings)
- nginx: reverse proxy for /api -> api:8000 and / -> frontend:3000
- docker-compose: full stack with shared data volume
- replace spec mc-domain-filter.md with README.md

api/Dockerfile

@@ -0,0 +1,13 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+
+COPY requirements.txt ./
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . ./
+
+ENV PYTHONUNBUFFERED=1
+EXPOSE 8000
+
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]