feat: realtime sync, settings UX and chat list improvements

- add chat_updated realtime event and dynamic chat subscriptions

- auto-join invite links in web app

- implement Telegram-like settings panel (general/notifications/privacy)

- add browser notification preferences and keyboard send mode

- improve chat list with last message preview/time and online badge

- rework chat members UI with context actions and role crowns

app/chats/schemas.py

@@ -3,6 +3,7 @@ from datetime import datetime
 from pydantic import BaseModel, ConfigDict, Field
 
 from app.chats.models import ChatMemberRole, ChatType
+from app.messages.models import MessageType
 
 
 class ChatRead(BaseModel):
@@ -29,6 +30,9 @@ class ChatRead(BaseModel):
     counterpart_username: str | None = None
     counterpart_is_online: bool | None = None
     counterpart_last_seen_at: datetime | None = None
+    last_message_text: str | None = None
+    last_message_type: MessageType | None = None
+    last_message_created_at: datetime | None = None
     my_role: ChatMemberRole | None = None
     created_at: datetime