feat(backend): 更新核心模块和文件处理

- 更新配置模块 (config.py)
- 更新数据库连接 (database.py)
- 更新主应用入口 (main.py)
- 更新数据模型 (models.py)
- 更新基础 Schema (base.py)
- 更新文件处理器 (docx, excel, pdf)
- 更新 Dockerfile

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/Dockerfile

@@ -1,27 +1,60 @@
-FROM python:3.11-slim
+# Multi-stage build for Python FastAPI application
+
+# Stage 1: Base image
+FROM python:3.11-slim as base
+
+# Set environment variables
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PYTHONFAULTHANDLER=1 \
+    PIP_NO_CACHE_DIR=1 \
+    PIP_DISABLE_PIP_VERSION_CHECK=1
 
 WORKDIR /app
 
+# Stage 2: Dependencies
+FROM base as deps
+
 # Install system dependencies
-RUN apt-get update && apt-get install -y \
+RUN apt-get update && apt-get install -y --no-install-recommends \
     build-essential \
     libpq-dev \
     && rm -rf /var/lib/apt/lists/*
 
-# Copy requirements
-COPY requirements.txt .
+# Create virtual environment
+RUN python -m venv /opt/venv
+ENV PATH="/opt/venv/bin:$PATH"
 
 # Install Python dependencies
+COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
-# Copy application
-COPY . .
 
-# Create uploads directory
-RUN mkdir -p uploads
+# Stage 3: Production
+FROM base
+
+# Install system dependencies for production
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libpq5 \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy virtual environment from deps stage
+COPY --from=deps /opt/venv /opt/venv
+ENV PATH="/opt/venv/bin:$PATH"
+
+# Copy application
+COPY --chown=app:app . /app
+RUN mkdir -p /app/uploads /app/logs && chown -R app:app /app
+
+# Switch to non-root user
+USER app
 
 # Expose port
 EXPOSE 8000
 
+# Health check
+HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
+    CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/health')" || exit 1
+
 # Run application
-CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--reload"]
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--workers", "4"]