Add and use https://github.com/ElMassimo/js_from_routes

On a des dépendances front-back qui peuvent créer des soucis, du style :
Si on change dans le back 'se-connecter' par 'login', le front va casser car il appelle en dur 'router.get('/se-connecter')

https://github.com/ElMassimo/js_from_routes

The issue names no files or tests. Start by locating the backend route definitions and the frontend calls such as router.get('/se-connecter'), then read the js_from_routes project linked in the issue. Done means frontend route references are generated or shared instead of hard-coded, so renaming a backend route no longer breaks them.

Written by the indexing model from the issue text.