feat(electron): 添加Electron桌面应用支持

- 新增Electron主进程、预加载脚本和构建配置
- 修改前端配置以支持Electron打包
- 更新项目文档和依赖
- 重构API调用使用统一axios实例

app/electron-builder.json

@@ -0,0 +1,39 @@
+{
+  "productName": "投标应用",
+  "appId": "com.bidding.app",
+  "directories": {
+    "output": "dist-electron",
+    "app": "./app"
+  },
+  "files": [
+    "dist/**/*",
+    "frontend/**/*",
+    ".env",
+    "node_modules/**/*",
+    "package.json",
+    "app/**/*"
+  ],
+  "win": {
+    "target": "nsis",
+    "icon": "frontend/public/favicon.ico",
+    "requestedExecutionLevel": "asInvoker"
+  },
+  "nsis": {
+    "oneClick": false,
+    "allowToChangeInstallationDirectory": true,
+    "createDesktopShortcut": true,
+    "createStartMenuShortcut": true,
+    "shortcutName": "投标应用"
+  },
+  "extraResources": [
+    {
+      "from": ".env",
+      "to": ".env",
+      "filter": ["**/*"]
+    }
+  ],
+  "publish": {
+    "provider": "generic",
+    "url": "http://localhost:3000/"
+  }
+}