🚚(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

.github/ISSUE_TEMPLATE/Bug_report.md

@@ -18,7 +18,7 @@ A clear and concise description of what you expected to happen (or code).
 3. And then the bug happens!
 
 **Environment**
-- Impress version:
+- Meet version:
 - Platform:
 
 **Possible Solution**