🚚(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

bin/update_openapi_schema

@@ -7,6 +7,6 @@ _dc_run \
     app-dev \
     python manage.py spectacular \
     --api-version 'v1.0' \
-    --urlconf 'impress.api_urls' \
+    --urlconf 'meet.api_urls' \
     --format openapi-json \
     --file /app/core/tests/swagger/swagger.json