🚚(backend) rename Impress to Meet

I have updated all references of "Impress" to "Meet".
Migrations were manually updated and not regenerated. Never-mind,
they all will be squashed before the first release.

I have also searched for reference to "Magnify", and replaced them
by "Meet".

While updating the backend sources, I have also fixed other parts of
the project, namely:
- Compose file
- Github documentation and CI
- Makefile commands

src/backend/core/tests/authentication/test_backends.py

@@ -64,7 +64,7 @@ def test_authentication_getter_new_user_with_email(monkeypatch):
     """
     klass = OIDCAuthenticationBackend()
 
-    email = "impress@example.com"
+    email = "meet@example.com"
 
     def get_userinfo_mocked(*args):
         return {"sub": "123", "email": email, "first_name": "John", "last_name": "Doe"}