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/messages/router.py

@@ -5,6 +5,7 @@ from app.auth.service import get_current_user
 from app.database.session import get_db
 from app.messages.schemas import MessageCreateRequest, MessageRead, MessageUpdateRequest
 from app.messages.service import create_chat_message, delete_message, get_messages, update_message
+from app.realtime.service import realtime_gateway
 from app.users.models import User
 
 router = APIRouter(prefix="/messages", tags=["messages"])
@@ -16,7 +17,9 @@ async def create_message(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> MessageRead:
-    return await create_chat_message(db, sender_id=current_user.id, payload=payload)
+    message = await create_chat_message(db, sender_id=current_user.id, payload=payload)
+    await realtime_gateway.publish_message_created(message=message, sender_id=current_user.id)
+    return message
 
 
 @router.get("/{chat_id}", response_model=list[MessageRead])