feat: 添加推送通知功能，支持Web Push订阅和发送

app/api/push/test/route.ts

@@ -0,0 +1,12 @@
+import { NextResponse } from 'next/server';
+import { push } from '@/lib/push';
+
+export async function POST() {
+  try {
+    push('这是一条测试推送消息 / This is a test push notification');
+    return NextResponse.json({ success: true });
+  } catch (error) {
+    console.error('Test push failed:', error);
+    return NextResponse.json({ error: 'Test push failed' }, { status: 500 });
+  }
+}