feat: 完成 Web2App 核心功能实现

- Electron 主进程：窗口管理、IPC、项目读写、打包引擎
- Vue 3 前端：4 个视图页面、3 个组件、Pinia 状态管理
- 生成应用模板：Express 后端 + Electron 窗口
- 支持资源导入、应用配置、跨平台打包

electron/preload.js

@@ -0,0 +1,30 @@
+const { contextBridge, ipcRenderer } = require('electron')
+
+contextBridge.exposeInMainWorld('api', {
+  dialog: {
+    selectDirectory: () => ipcRenderer.invoke('dialog:selectDirectory'),
+    selectFile: (options) => ipcRenderer.invoke('dialog:selectFile', options),
+    selectIcon: () => ipcRenderer.invoke('dialog:selectIcon'),
+    saveFile: (options) => ipcRenderer.invoke('dialog:saveFile', options)
+  },
+  dir: {
+    readTree: (dirPath) => ipcRenderer.invoke('dir:readTree', dirPath)
+  },
+  project: {
+    create: (name, dir) => ipcRenderer.invoke('project:create', name, dir),
+    load: (projectPath) => ipcRenderer.invoke('project:load', projectPath),
+    save: (projectPath, data) => ipcRenderer.invoke('project:save', projectPath, data),
+    importFiles: (projectPath, files) => ipcRenderer.invoke('project:importFiles', projectPath, files),
+    removeFile: (projectPath, relativePath) => ipcRenderer.invoke('project:removeFile', projectPath, relativePath),
+    setIcon: (projectPath, iconPath) => ipcRenderer.invoke('project:setIcon', projectPath, iconPath)
+  },
+  pack: {
+    start: (projectPath, outputPath) => ipcRenderer.invoke('pack:start', projectPath, outputPath),
+    cancel: () => ipcRenderer.invoke('pack:cancel'),
+    onProgress: (callback) => {
+      const handler = (_event, progress) => callback(progress)
+      ipcRenderer.on('pack:progress', handler)
+      return () => ipcRenderer.removeListener('pack:progress', handler)
+    }
+  }
+})