Refactor wger config to use .env and environment variables

Replaces the custom settings directory with a .env file for configuration. Updates backup and restore logic to handle .env instead of settings, and sets required Django environment variables explicitly. Simplifies installation and update scripts for better maintainability and security.

install/wger-install.sh

@@ -33,23 +33,18 @@ chmod o+w /opt/wger/media
 cd /opt/wger
 $STD uv venv
 $STD uv pip install .
-mkdir -p /opt/wger/settings
-cat <<EOF >/opt/wger/settings/main.py
-from wger.settings_global import *
-
-DATABASES = {
-    'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': '/opt/wger/db/database.sqlite',
-    }
-}
-
-MEDIA_ROOT = '/opt/wger/media'
-STATIC_ROOT = '/opt/wger/static'
+SECRET_KEY=$(openssl rand -base64 40)
+cat <<EOF >/opt/wger/.env
+DJANGO_DB_DATABASE=/opt/wger/db/database.sqlite
+DJANGO_MEDIA_ROOT=/opt/wger/media
+DJANGO_STATIC_ROOT=/opt/wger/static
+SECRET_KEY=${SECRET_KEY}
 EOF
-touch /opt/wger/settings/__init__.py
 export DJANGO_SETTINGS_MODULE=settings.main
-export PYTHONPATH=/opt/wger
+export DJANGO_DB_DATABASE=/opt/wger/db/database.sqlite
+export DJANGO_MEDIA_ROOT=/opt/wger/media
+export DJANGO_STATIC_ROOT=/opt/wger/static
+export SECRET_KEY="${SECRET_KEY}"
 $STD uv run python manage.py migrate
 $STD uv run python manage.py collectstatic --no-input
 msg_ok "Set up wger"
@@ -69,7 +64,10 @@ cat <<EOF >/etc/apache2/sites-available/wger.conf
     WSGIScriptAlias / /opt/wger/wger/wsgi.py
     WSGIPassAuthorization On
     SetEnv DJANGO_SETTINGS_MODULE settings.main
-    SetEnv PYTHONPATH /opt/wger
+    SetEnv DJANGO_DB_DATABASE /opt/wger/db/database.sqlite
+    SetEnv DJANGO_MEDIA_ROOT /opt/wger/media
+    SetEnv DJANGO_STATIC_ROOT /opt/wger/static
+    SetEnv SECRET_KEY ${SECRET_KEY}
 
     Alias /static/ /opt/wger/static/
     <Directory /opt/wger/static>