chore: 更新 Docker 部署配置及文档

Co-Authored-By: Claude <noreply@anthropic.com>

docker/app/Dockerfile.backend

@@ -11,6 +11,8 @@ RUN pip install --upgrade pip \
     && pip install -r /tmp/requirements.txt \
     && rm -f /tmp/requirements.txt
 
+RUN python -c "import fastapi, uvicorn, psycopg, sqlalchemy, redis, jwt, passlib, httpx, alembic; print('backend dependency check ok')"
+
 RUN mkdir -p /opt/yg-ft/logs/backend /data/yg-ft \
     && chmod -R 0775 /opt/yg-ft /data/yg-ft