🚚(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

env.d/development/postgresql.dist

@@ -1,11 +1,11 @@
 # Postgresql db container configuration
-POSTGRES_DB=impress
+POSTGRES_DB=meet
 POSTGRES_USER=dinum
 POSTGRES_PASSWORD=pass
 
 # App database configuration
 DB_HOST=postgresql
-DB_NAME=impress
+DB_NAME=meet
 DB_USER=dinum
 DB_PASSWORD=pass
 DB_PORT=5432