feat: 初始化 Timeline 桌面客户端基础框架

添加 Electron 应用基础结构，包括：
- package.json 配置文件
- 主进程和预加载脚本
- README 文档
- 自动更新功能
- 系统托盘和菜单
- IPC 通信机制

package.json

@@ -0,0 +1,72 @@
+{
+  "name": "timeline-desktop",
+  "version": "1.0.0",
+  "description": "Timeline 桌面客户端 - 记录生活中的每一个精彩时刻",
+  "main": "dist/main.js",
+  "author": "Timeline Team",
+  "license": "MIT",
+  "scripts": {
+    "dev": "electron-vite dev",
+    "build": "electron-vite build",
+    "preview": "electron-vite preview",
+    "pack": "electron-builder --dir",
+    "dist": "electron-builder",
+    "dist:win": "electron-builder --win",
+    "dist:mac": "electron-builder --mac",
+    "dist:linux": "electron-builder --linux"
+  },
+  "dependencies": {
+    "electron-updater": "^6.1.7",
+    "electron-store": "^8.1.0",
+    "axios": "^1.6.0",
+    "date-fns": "^3.2.0"
+  },
+  "devDependencies": {
+    "electron": "^28.1.0",
+    "electron-builder": "^24.9.1",
+    "electron-vite": "^2.0.0",
+    "vite": "^5.0.0",
+    "typescript": "^5.3.0",
+    "@types/node": "^20.10.0"
+  },
+  "build": {
+    "appId": "com.timeline.desktop",
+    "productName": "Timeline",
+    "directories": {
+      "output": "release"
+    },
+    "files": [
+      "dist/**/*",
+      "package.json"
+    ],
+    "mac": {
+      "category": "public.app-category.lifestyle",
+      "icon": "build/icon.icns",
+      "target": ["dmg", "zip"]
+    },
+    "win": {
+      "icon": "build/icon.ico",
+      "target": [
+        {
+          "target": "nsis",
+          "arch": ["x64", "ia32"]
+        }
+      ]
+    },
+    "linux": {
+      "icon": "build/icon.png",
+      "target": ["AppImage", "deb"]
+    },
+    "nsis": {
+      "oneClick": false,
+      "allowToChangeInstallationDirectory": true,
+      "createDesktopShortcut": true,
+      "createStartMenuShortcut": true
+    },
+    "publish": {
+      "provider": "github",
+      "owner": "timeline",
+      "repo": "timeline-desktop"
+    }
+  }
+}