🔧(backend) fix Pylint configurations

Removing the __init__.py makes it impossible for Pylint to get the sources
to lint from the root folder. We manually set all the paths pylint will lint.

That's not a big deal, as we'll remove Pylint any soon to rely only on ruff.
I took inspiration from marsha or magnify project.

I removed the now useless bash script to run Pylint command. It saves us
wrapper! Plus, having a lint command running with different option locally
and in the CI was quite a pain.

Locally linter was running on diff files; Fixed! CI and make command has now
the same behavior.

.github/workflows/meet.yml

@@ -89,7 +89,7 @@ jobs:
       - name: Lint code with ruff
         run: ~/.local/bin/ruff check .
       - name: Lint code with pylint
-        run: ~/.local/bin/pylint .
+        run: ~/.local/bin/pylint meet demo core
 
   test-back:
     runs-on: ubuntu-latest