feat: improve chat realtime and media composer UX

- add media preview and upload confirmation for image/video

- add upload progress tracking for presigned uploads

- keep voice recording/upload flow with better UI states

- include related realtime/chat updates currently in working tree

app/realtime/service.py

@@ -83,17 +83,7 @@ class RealtimeGateway:
             sender_id=user_id,
             payload=MessageCreateRequest(chat_id=payload.chat_id, type=payload.type, text=payload.text),
         )
-        message_data = MessageRead.model_validate(message).model_dump(mode="json")
-        await self._publish_chat_event(
-            payload.chat_id,
-            event="receive_message",
-            payload={
-                "chat_id": payload.chat_id,
-                "message": message_data,
-                "temp_id": payload.temp_id,
-                "sender_id": user_id,
-            },
-        )
+        await self.publish_message_created(message=message, sender_id=user_id, temp_id=payload.temp_id)
 
     async def handle_typing_event(self, db: AsyncSession, user_id: int, payload: ChatEventPayload, event: str) -> None:
         await ensure_chat_membership(db, chat_id=payload.chat_id, user_id=user_id)
@@ -149,6 +139,19 @@ class RealtimeGateway:
             return
         await self._handle_redis_event(f"chat:{chat_id}", event_payload)
 
+    async def publish_message_created(self, *, message, sender_id: int, temp_id: str | None = None) -> None:
+        message_data = MessageRead.model_validate(message).model_dump(mode="json")
+        await self._publish_chat_event(
+            message.chat_id,
+            event="receive_message",
+            payload={
+                "chat_id": message.chat_id,
+                "message": message_data,
+                "temp_id": temp_id,
+                "sender_id": sender_id,
+            },
+        )
+
     async def _send_user_event(self, user_id: int, event: OutgoingRealtimeEvent) -> None:
         user_connections = self._connections.get(user_id, {})
         if not user_connections: