feat: mongodb 单后端精简分支 — Beanie 2.x + pymongo async，移除 MySQL/alembic

Dockerfile

@@ -2,15 +2,12 @@ FROM python:3.12-slim
 
 WORKDIR /app
 
-# uv 管理依赖（国内构建加 --index-url 镜像）
 COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv
 
 COPY pyproject.toml uv.lock* ./
 RUN uv sync --no-dev --no-cache
 
 COPY src ./src
-COPY alembic ./alembic
-COPY alembic.ini ./
 
 EXPOSE 8000
 CMD ["uv", "run", "--no-sync", "uvicorn", "src.main:app", "--host", "0.0.0.0", "--port", "8000"]