fix: Windows compatibility and startup scripts

- Add explicit .env loading in config.py for Windows compatibility
- Add backend directory to sys.path in main.py to fix module imports
- Add start.bat and start-full.bat for Windows startup
- Add frontend/package-lock.json for dependency tracking

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

start.bat

@@ -0,0 +1,46 @@
+@echo off
+chcp 65001 >nul
+echo ========================================
+echo   Git Repo Manager - Windows 启动脚本
+echo ========================================
+echo.
+
+REM 检查 .env 文件
+if not exist ".env" (
+    echo [错误] .env 文件不存在！
+    echo.
+    echo 请先复制 .env.example 到 .env 并配置密钥:
+    echo   copy .env.example .env
+    echo.
+    pause
+    exit /b 1
+)
+
+echo [1/5] 检查 .env 文件... ✓
+echo.
+
+REM 检查数据库
+if not exist "data\git_manager.db" (
+    echo [2/5] 数据库不存在，正在初始化...
+    python -m backend.init_db
+    if errorlevel 1 (
+        echo [错误] 数据库初始化失败！
+        pause
+        exit /b 1
+    )
+) else (
+    echo [2/5] 数据库已存在... ✓
+)
+echo.
+
+REM 启动后端服务
+echo [3/5] 启动后端服务...
+echo.
+echo 后端地址: http://%GM_HOST%:%GM_PORT%
+echo API 文档: http://%GM_HOST%:%GM_PORT%/docs
+echo.
+echo 按 Ctrl+C 停止服务
+echo ========================================
+echo.
+
+uvicorn backend.app.main:app --host %GM_HOST% --port %GM_PORT% --reload