feat: 添加轻量打包和OCR自动安装功能

- 添加Windows打包脚本 build.bat
- 更新打包文档 BUILD.md（轻量版方案）
- OCR模块：添加首次运行时自动安装PaddleOCR的功能
- 主窗口：添加OCR安装检测和提示逻辑
- 创建应用入口 src/main.py

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

build.sh

@@ -0,0 +1,71 @@
+#!/bin/bash
+# CutThenThink 简化打包脚本
+
+set -e
+
+echo "==================================="
+echo "CutThenThink 打包脚本"
+echo "==================================="
+
+# 使用系统Python和pip
+PYTHON="python3"
+PIP="python3 -m pip"
+
+echo ""
+echo "1/4. 安装打包工具..."
+$PIP install --user pyinstaller 2>/dev/null || echo "   PyInstaller可能已安装"
+
+echo ""
+echo "2/4. 安装项目依赖..."
+$PIP install --user -r requirements.txt 2>/dev/null || echo "   依赖可能已安装"
+
+echo ""
+echo "3/4. 创建应用入口（如果不存在）..."
+if [ ! -f "src/main.py" ]; then
+    cat > src/main.py << 'PYEOF'
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+CutThenThink 应用入口
+"""
+import sys
+import os
+
+# 添加src目录到路径
+current_dir = os.path.dirname(os.path.abspath(__file__))
+sys.path.insert(0, current_dir)
+
+from gui.main_window import main
+
+if __name__ == "__main__":
+    main()
+PYEOF
+fi
+
+echo ""
+echo "4/4. 开始打包..."
+$PYTHON -m PyInstaller \
+    --name "CutThenThink" \
+    --windowed \
+    --onefile \
+    --add-data "src:src" \
+    --hidden-import=PyQt6.QtCore \
+    --hidden-import=PyQt6.QtGui \
+    --hidden-import=PyQt6.QtWidgets \
+    --hidden-import=sqlalchemy \
+    src/main.py
+
+echo ""
+echo "==================================="
+echo "打包完成！"
+echo "可执行文件: dist/CutThenThink"
+echo "==================================="
+
+# 测试运行提示
+echo ""
+read -p "是否测试运行？(y/n) " -n 1 -r
+echo
+if [[ $REPLY =~ ^[Yy]$ ]]; then
+    echo "启动测试..."
+    ./dist/CutThenThink
+fi