chore(backend): 迁移包管理工具从 pip 到 uv

- 新增 pyproject.toml 替代 requirements.txt，合并 pytest.ini 配置
- 添加 greenlet、httpx[socks] 依赖修复运行时错误
- 添加 basedpyright + ruff 开发工具及配置
- 更新 Dockerfile 使用 uv 安装依赖
- 更新 CLAUDE.md 所有后端命令为 uv 前缀
- 删除 requirements.txt 和 pytest.ini

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/Dockerfile

@@ -1,5 +1,7 @@
 FROM python:3.11-slim
 
+COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /bin/
+
 WORKDIR /app
 
 # Install system dependencies
@@ -8,9 +10,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     libpq-dev \
     && rm -rf /var/lib/apt/lists/*
 
-# Copy requirements and install Python dependencies
-COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
+# Copy dependency files and install
+COPY pyproject.toml uv.lock ./
+RUN uv sync --frozen --no-dev --no-install-project
 
 # Copy application code
 COPY app/ ./app/
@@ -27,4 +29,4 @@ HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
     CMD curl -f http://localhost:8000/health || exit 1
 
 # Start application
-CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]
+CMD ["uv", "run", "uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]