feat(video-lab): Dockerfile + requirements + app package skeleton (SP-8)

NAS video-lab 신설. python:3.12-alpine 기반. redis>=5.0 의존성.
영상 외부 호출 없음(gateway만) — 외부 API 의존 없음.
Plan-B-Video Phase 1.

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

video-lab/Dockerfile

@@ -0,0 +1,10 @@
+FROM python:3.12-alpine
+ENV PYTHONUNBUFFERED=1
+
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--workers", "1"]