🚨(CI) fix linter backend

The linter in the CI was checking only the
impress directory. We were passing near some lint
issues. Now the linter checks the whole backend
directory.

src/backend/demo/management/commands/create_demo.py

@@ -1,7 +1,6 @@
 # ruff: noqa: S311, S106
 """create_demo management command"""
 
-import json
 import logging
 import random
 import time
@@ -110,10 +109,14 @@ def create_demo(stdout):
     queue = BulkQueue(stdout)
 
     with Timeit(stdout, "Creating Template"):
-        with open("demo/data/template/code.txt", "r") as text_file:
+        with open(
+            file="demo/data/template/code.txt", mode="r", encoding="utf-8"
+        ) as text_file:
             code_data = text_file.read()
 
-        with open("demo/data/template/css.txt", "r") as text_file:
+        with open(
+            file="demo/data/template/css.txt", mode="r", encoding="utf-8"
+        ) as text_file:
             css_data = text_file.read()
 
         queue.push(

src/backend/demo/tests/test_commands_create_demo.py

@@ -1,7 +1,5 @@
 """Test the `create_demo` management command"""
 
-from unittest import mock
-
 from django.core.management import call_command
 from django.test import override_settings