feat(realtime): live online/offline events and unified search

- add websocket events user_online/user_offline
- broadcast presence changes on first connect and final disconnect only
- apply live presence updates in web chat store and realtime hook
- move public discover into unified left search (users + groups/channels)
- remove separate Discover Chats dialog/menu entry

app/realtime/presence.py

@@ -3,26 +3,30 @@ from redis.exceptions import RedisError
 from app.utils.redis_client import get_redis_client
 
 
-async def mark_user_online(user_id: int) -> None:
+async def mark_user_online(user_id: int) -> bool:
     try:
         redis = get_redis_client()
         key = f"presence:user:{user_id}"
         count = await redis.incr(key)
         if count == 1:
             await redis.expire(key, 3600)
+            return True
+        return False
     except RedisError:
-        return
+        return False
 
 
-async def mark_user_offline(user_id: int) -> None:
+async def mark_user_offline(user_id: int) -> bool:
     try:
         redis = get_redis_client()
         key = f"presence:user:{user_id}"
         value = await redis.decr(key)
         if value <= 0:
             await redis.delete(key)
+            return True
+        return False
     except RedisError:
-        return
+        return False
 
 
 async def is_user_online(user_id: int) -> bool:

app/realtime/schemas.py

@@ -15,6 +15,8 @@ RealtimeEventName = Literal[
     "typing_stop",
     "message_read",
     "message_delivered",
+    "user_online",
+    "user_offline",
     "error",
 ]
 

app/realtime/service.py

@@ -54,7 +54,9 @@ class RealtimeGateway:
         )
         for chat_id in user_chat_ids:
             self._chat_subscribers[chat_id].add(user_id)
-        await mark_user_online(user_id)
+        became_online = await mark_user_online(user_id)
+        if became_online:
+            await self._broadcast_presence(user_chat_ids, user_id=user_id, is_online=True, last_seen_at=None)
         await self._send_user_event(
             user_id,
             OutgoingRealtimeEvent(
@@ -77,8 +79,15 @@ class RealtimeGateway:
                 subscribers.discard(user_id)
                 if not subscribers:
                     self._chat_subscribers.pop(chat_id, None)
-            await mark_user_offline(user_id)
+            became_offline = await mark_user_offline(user_id)
             await self._persist_last_seen(user_id)
+            if became_offline:
+                await self._broadcast_presence(
+                    user_chat_ids,
+                    user_id=user_id,
+                    is_online=False,
+                    last_seen_at=datetime.now(timezone.utc),
+                )
 
     async def handle_send_message(self, db: AsyncSession, user_id: int, payload: SendMessagePayload) -> None:
         message = await create_chat_message(
@@ -195,12 +204,22 @@ class RealtimeGateway:
             user_connections.pop(connection_id, None)
         if not user_connections:
             self._connections.pop(user_id, None)
+            affected_chat_ids: list[int] = []
             for chat_id, subscribers in list(self._chat_subscribers.items()):
+                if user_id in subscribers:
+                    affected_chat_ids.append(chat_id)
                 subscribers.discard(user_id)
                 if not subscribers:
                     self._chat_subscribers.pop(chat_id, None)
-            await mark_user_offline(user_id)
+            became_offline = await mark_user_offline(user_id)
             await self._persist_last_seen(user_id)
+            if became_offline:
+                await self._broadcast_presence(
+                    affected_chat_ids,
+                    user_id=user_id,
+                    is_online=False,
+                    last_seen_at=datetime.now(timezone.utc),
+                )
 
     @staticmethod
     def _extract_chat_id(channel: str) -> int | None:
@@ -219,5 +238,24 @@ class RealtimeGateway:
         except Exception:
             return
 
+    async def _broadcast_presence(
+        self,
+        chat_ids: list[int],
+        *,
+        user_id: int,
+        is_online: bool,
+        last_seen_at: datetime | None,
+    ) -> None:
+        event_name = "user_online" if is_online else "user_offline"
+        for chat_id in chat_ids:
+            payload = {
+                "chat_id": chat_id,
+                "user_id": user_id,
+                "is_online": is_online,
+            }
+            if last_seen_at is not None:
+                payload["last_seen_at"] = last_seen_at.isoformat()
+            await self._publish_chat_event(chat_id, event=event_name, payload=payload)
+
 
 realtime_gateway = RealtimeGateway()