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/router.py

@@ -43,6 +43,7 @@ from app.chats.service import (
     update_chat_title_for_user,
 )
 from app.database.session import get_db
+from app.realtime.service import realtime_gateway
 from app.users.models import User
 
 router = APIRouter(prefix="/chats", tags=["chats"])
@@ -94,6 +95,7 @@ async def create_chat(
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
     chat = await create_chat_for_user(db, creator_id=current_user.id, payload=payload)
+    realtime_gateway.add_chat_subscription(chat_id=chat.id, user_id=current_user.id)
     return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
@@ -104,6 +106,8 @@ async def join_chat(
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
     chat = await join_public_chat_for_user(db, chat_id=chat_id, user_id=current_user.id)
+    realtime_gateway.add_chat_subscription(chat_id=chat.id, user_id=current_user.id)
+    await realtime_gateway.publish_chat_updated(chat_id=chat.id)
     return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
@@ -131,6 +135,7 @@ async def update_chat_title(
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
     chat = await update_chat_title_for_user(db, chat_id=chat_id, user_id=current_user.id, payload=payload)
+    await realtime_gateway.publish_chat_updated(chat_id=chat.id)
     return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
@@ -151,7 +156,10 @@ async def add_chat_member(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> ChatMemberRead:
-    return await add_chat_member_for_user(db, chat_id=chat_id, actor_user_id=current_user.id, target_user_id=payload.user_id)
+    member = await add_chat_member_for_user(db, chat_id=chat_id, actor_user_id=current_user.id, target_user_id=payload.user_id)
+    realtime_gateway.add_chat_subscription(chat_id=chat_id, user_id=payload.user_id)
+    await realtime_gateway.publish_chat_updated(chat_id=chat_id)
+    return member
 
 
 @router.patch("/{chat_id}/members/{user_id}/role", response_model=ChatMemberRead)
@@ -162,13 +170,15 @@ async def update_chat_member_role(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> ChatMemberRead:
-    return await update_chat_member_role_for_user(
+    member = await update_chat_member_role_for_user(
         db,
         chat_id=chat_id,
         actor_user_id=current_user.id,
         target_user_id=user_id,
         role=payload.role,
     )
+    await realtime_gateway.publish_chat_updated(chat_id=chat_id)
+    return member
 
 
 @router.delete("/{chat_id}/members/{user_id}", status_code=status.HTTP_204_NO_CONTENT)
@@ -179,6 +189,8 @@ async def remove_chat_member(
     current_user: User = Depends(get_current_user),
 ) -> None:
     await remove_chat_member_for_user(db, chat_id=chat_id, actor_user_id=current_user.id, target_user_id=user_id)
+    realtime_gateway.remove_chat_subscription(chat_id=chat_id, user_id=user_id)
+    await realtime_gateway.publish_chat_updated(chat_id=chat_id)
 
 
 @router.post("/{chat_id}/leave", status_code=status.HTTP_204_NO_CONTENT)
@@ -188,6 +200,8 @@ async def leave_chat(
     current_user: User = Depends(get_current_user),
 ) -> None:
     await leave_chat_for_user(db, chat_id=chat_id, user_id=current_user.id)
+    realtime_gateway.remove_chat_subscription(chat_id=chat_id, user_id=current_user.id)
+    await realtime_gateway.publish_chat_updated(chat_id=chat_id)
 
 
 @router.delete("/{chat_id}", status_code=status.HTTP_204_NO_CONTENT)
@@ -217,6 +231,7 @@ async def pin_chat_message(
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
     chat = await pin_chat_message_for_user(db, chat_id=chat_id, user_id=current_user.id, payload=payload)
+    await realtime_gateway.publish_chat_updated(chat_id=chat.id)
     return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
@@ -300,4 +315,6 @@ async def join_by_invite(
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
     chat = await join_chat_by_invite_for_user(db, user_id=current_user.id, payload=payload)
+    realtime_gateway.add_chat_subscription(chat_id=chat.id, user_id=current_user.id)
+    await realtime_gateway.publish_chat_updated(chat_id=chat.id)
     return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)