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

web/src/chat/types.ts

@@ -24,6 +24,9 @@ export interface Chat {
   counterpart_username?: string | null;
   counterpart_is_online?: boolean | null;
   counterpart_last_seen_at?: string | null;
+  last_message_text?: string | null;
+  last_message_type?: MessageType | null;
+  last_message_created_at?: string | null;
   my_role?: ChatMemberRole | null;
   created_at: string;
 }
@@ -102,6 +105,7 @@ export interface ChatAttachment {
   id: number;
   message_id: number;
   sender_id: number;
+  message_type: MessageType;
   message_created_at: string;
   file_url: string;
   file_type: string;