🎨 飞行侠添加：Web 界面

新增:
- templates/meeting_room.html: 完整 Web 界面
  - 用户登录/注册
  - 创建/加入会议
  - 发送消息
  - Agent 模式（查信箱 + 回复）
  - 实时消息列表
- urls.py: 添加首页路由

访问地址：http://localhost:8000/

backend/meeting_room/urls.py

@@ -1,5 +1,6 @@
 from django.contrib import admin
 from django.urls import path, include
+from django.views.generic import TemplateView
 from rest_framework.routers import DefaultRouter
 from meetings.views import MeetingViewSet, ParticipantViewSet
 from users.views import LoginView, RegisterView
@@ -10,6 +11,7 @@ router.register(r'meetings/(?P<meeting_pk>[^/.]+)/participants', ParticipantView
 
 urlpatterns = [
     path("admin/", admin.site.urls),
+    path("", TemplateView.as_view(template_name="meeting_room.html"), name="home"),
     path("api/v1/", include(router.urls)),
     path("api/v1/auth/login/", LoginView.as_view()),
     path("api/v1/auth/register/", RegisterView.as_view()),