This functionality was lost when moving to a template-based approach for
the list of all translators.

Fixes #32

Only on mobile FF apparently, maybe some side effect of turbo morph?

Includes hamburger menu ✨

This dramatically speeds up rendering with many translators.

This is more consistent and actually removes the elements from the layout.

The commit also hides the conditional elements by default, which should
be a more natural loading experience.

The state is now fully client-side and handled in session_controller.
This allows us to continue to broadcast the session frame to everyone.

- Add X button to clear filter
- Restrict maximum height
- Visually group list with filter input