docker: ensure the server can see the .hotfile from the new frontend

The `.hotfile` is used by Vite to store some information about
Hot-Module Replacement (HMR) and also by the django-vite-plugin to
figure out whether Vite is running[1]; this creates a filesystem
dependency where 2024-frontend has to write the hotfile and the server
has to read it. But now that we git-ignore[2] the hotfile (which is a
good idea) the server couldn't see the file anymore.

Before:

1. We built the server Docker image with all the files in it;
2. We built the 2024-frontend image based on it;
3. It had a (stale) `.hotfile` included because we tracked it.

After the ignore:

1. We built the server Docker images without the hotfile ;
2. We built the 2024-frontend image based on it;
3. The hotfile was not present because 2024-frontend writes it to
`../app` but since we only mounted `2024-frontend` into
`/app/2024-frontend` the parent folder is not shared: no hotfile,
everybody gets sad.

Now:

1. We share the whole current folder into `.:/app`, which means the
2024-frontend writes the hotfile up into `../` and the server sees it;
2. Things work as expected.

[1]: https://github.com/protibimbok/django-vite-plugin/blob/master/django/src/django_vite_plugin/utils.py#L120-L124
[2]: 0687770

compose.yaml

@@ -41,7 +41,7 @@ services:
       context: 2024-frontend
     image: ma-cantine-2024-front
     volumes:
-      - "./2024-frontend:/app/2024-frontend"
+      - "./:/app"
       - "/app/2024-frontend/node_modules"
     ports:
       - 5173:5173