feat: 添加安装向导功能

- 后端：安装状态检测API、数据库连接测试、配置文件生成
- 后端：支持SQLite/MySQL数据库选择
- 后端：JWT密钥自动生成或手动设置
- 前端：安装向导界面（数据库配置、安全配置、管理员账号）
- 前端：路由守卫检测安装状态，未安装自动跳转安装页面

frontend/src/router/guard/index.ts

@@ -1,7 +1,35 @@
 import type { Router } from 'vue-router'
 
+let installChecked = false
+let isInstalled = false
+
+async function checkInstallStatus(): Promise<boolean> {
+  if (installChecked) return isInstalled
+  try {
+    const res = await fetch('/api/install/status')
+    const data = await res.json()
+    isInstalled = data?.data?.installed || false
+    installChecked = true
+    return isInstalled
+  }
+  catch {
+    installChecked = true
+    isInstalled = true
+    return true
+  }
+}
+
 export function createRouterGuard(router: Router) {
-  router.beforeEach((to) => {
+  router.beforeEach(async (to) => {
+    if (to.path === '/install') {
+      return true
+    }
+
+    const installed = await checkInstallStatus()
+    if (!installed) {
+      return '/install'
+    }
+
     const token = localStorage.getItem('token')
     const userStr = localStorage.getItem('user')