[UX] Mensajes de Feedback con Django Messages 💬

Cuando alguien se une a una sala o envía sus frases, no hay una confirmación visual de 'Éxito'. Tarea: Implementar django.contrib.messages para mostrar notificaciones flotantes (Toasts) al realizar acciones clave.

First locate the Django views or entry points for joining a room and submitting phrases, then find the templates that render those responses. Trace the existing Django configuration and template layout before adding django.contrib.messages and the toast presentation. Done means both key actions show clear success feedback in the interface.

Written by the indexing model from the issue text.