fix: 完善动态错误指引与发票日期校验（09-05-error-explainability-payment-readiness）

server/tests/unit/routes/me.test.js

@@ -188,4 +188,17 @@ describe('me routes', () => {
 
     await app.close();
   });
+
+  it('explains invalid notification settings without changing preferences', async () => {
+    const { prisma, auditEntries } = createPrismaState();
+    const app = await buildApp(prisma);
+    try {
+      const response = await app.inject({ method: 'PATCH', url: '/api/me/notification-preferences',
+        headers: { authorization: 'Bearer test-token' }, payload: { notificationPushEnabled: 'false' } });
+      expect(response.statusCode).toBe(400);
+      expect(response.json().error.details.reasonCode).toBe('profile.notification_preferences_invalid');
+      expect(prisma.employee.update).not.toHaveBeenCalled();
+      expect(auditEntries).toHaveLength(0);
+    } finally { await app.close(); }
+  });
 });