Fix STATIC_ROOT configuration and improve production settings

- Add STATIC_ROOT and MEDIA_ROOT settings with environment variable support
- Update settings.py to use environment variables for SECRET_KEY, DEBUG, ALLOWED_HOSTS, TIME_ZONE
- Improve docker-entrypoint.sh to auto-create static/media directories
- Always run collectstatic in Docker (not just production)
- Add check_settings.py script for configuration verification
- Add PRODUCTION_CHECKLIST.md for deployment guide
- Update .env.example with all configuration options
- Update .gitignore for proper static/media file handling

This fixes the ImproperlyConfigured error when deploying with Docker.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

docker-entrypoint.sh

@@ -2,6 +2,13 @@
 set -e
 
 echo "Starting Django application..."
+echo "Environment: ${DJANGO_ENV:-development}"
+echo ""
+
+# 정적/미디어 파일 디렉토리 생성
+echo "Creating directories..."
+mkdir -p /app/staticfiles
+mkdir -p /app/mediafiles
 
 # 데이터베이스 마이그레이션
 echo "Running database migrations..."
@@ -11,11 +18,13 @@ python manage.py migrate --noinput
 echo "Initializing strategies..."
 python manage.py init_strategies
 
-# 정적 파일 수집 (production 환경에서만)
-if [ "$DJANGO_ENV" = "production" ]; then
-    echo "Collecting static files..."
-    python manage.py collectstatic --noinput
-fi
+# 정적 파일 수집
+echo "Collecting static files..."
+python manage.py collectstatic --noinput --clear
+
+echo ""
+echo "Django application ready!"
+echo ""
 
 # 전달된 명령어 실행
 exec "$@"