v2.0.0: 主题系统+SSH私钥解析修复+会话持久化+连接池优化+UI打磨

核心修复:
- ssh-service.ts: 新增 resolvePrivateKey()，将私钥文件路径(~/.ssh/id_rsa)解析为内容后传给 ssh2，
  解决 'Cannot parse privateKey: Unsupported key format' 错误
- useTerminalConnection.ts + sessionHelper.ts: 根据 authType 过滤字段，password/agent 认证不再传 privateKey
- sessionStore.ts: addSession() 现在先调用 sessionCreate() 持久化到 SQLite，解决恢复标签'无可用连接信息'问题
- database-service.ts: updateSession() 补充 private_key_path 字段持久化
- SessionDialog.tsx: 默认 username='root'、privateKey='~/.ssh/id_rsa'

UI/UX:
- 语义化主题系统(app-theme.ts)，强制深色模式，全局无边框设计
- macOS 标题栏支持双击最大化(window:toggleMaximize IPC)
- macOS 菜单栏('OpsXShell' 应用菜单 + Settings Cmd+,)
- WelcomeView 4卡片布局，移除 Settings 按钮
- TabBar/TabItem 背景色统一(bg-dark-800/900)，消除白色边框线

架构优化:
- SFTP 生命周期修复(useSFTP.ts useRef + autoConnectAttempted guard)
- 连接池竞态修复，支持快速多标签连接
- IPC 接口规范化，安全错误处理
- Vite 代码分割优化

质量: lint零错误 | tsc零错误 | build成功 | 49 tests pass

electron/ipc/index.ts

@@ -16,9 +16,10 @@ import { registerSFTPIPCHandlers } from './sftp.ipc'
 import { registerSessionIPCHandlers } from './session.ipc'
 import { registerSettingsIPCHandlers } from './settings.ipc'
 import { registerDialogIPCHandlers } from './dialog.ipc'
-import { registerFileIPCHandlers } from './file.ipc'
+import { registerFileIPCHandlers, initializeAllowedPaths } from './file.ipc'
 import { registerZmodemIPCHandlers } from './zmodem.ipc'
 import { registerAppIPCHandlers } from './app.ipc'
+import { ipcMain } from 'electron'
 
 export interface IPCOptions {
   sshService: SSHService
@@ -45,7 +46,8 @@ export function registerAllIPCHandlers(options: IPCOptions): void {
   // Dialog handlers
   registerDialogIPCHandlers({ mainWindowGetter })
 
-  // File handlers
+  // File handlers (初始化路径白名单)
+  initializeAllowedPaths()
   registerFileIPCHandlers()
 
   // Zmodem handlers
@@ -54,6 +56,17 @@ export function registerAllIPCHandlers(options: IPCOptions): void {
   // App handlers
   registerAppIPCHandlers()
 
+  // Window handlers
+  ipcMain.handle('window:toggleMaximize', () => {
+    const win = mainWindowGetter()
+    if (!win) return
+    if (win.isMaximized()) {
+      win.unmaximize()
+    } else {
+      win.maximize()
+    }
+  })
+
   logger.info('[IPC] All handlers registered')
 }