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>

check_settings.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python
+"""Django 설정 확인 스크립트"""
+
+import os
+import django
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'executor.settings')
+django.setup()
+
+from django.conf import settings
+
+print("="*80)
+print("Django 설정 확인")
+print("="*80)
+print()
+
+print("기본 설정:")
+print(f"  DEBUG: {settings.DEBUG}")
+print(f"  SECRET_KEY: {'***' + settings.SECRET_KEY[-10:] if len(settings.SECRET_KEY) > 10 else '***'}")
+print(f"  ALLOWED_HOSTS: {settings.ALLOWED_HOSTS}")
+print()
+
+print("데이터베이스:")
+print(f"  ENGINE: {settings.DATABASES['default']['ENGINE']}")
+print(f"  NAME: {settings.DATABASES['default']['NAME']}")
+print()
+
+print("정적 파일:")
+print(f"  STATIC_URL: {settings.STATIC_URL}")
+print(f"  STATIC_ROOT: {settings.STATIC_ROOT}")
+print(f"  STATIC_ROOT 존재: {os.path.exists(settings.STATIC_ROOT)}")
+print()
+
+print("미디어 파일:")
+print(f"  MEDIA_URL: {settings.MEDIA_URL}")
+print(f"  MEDIA_ROOT: {settings.MEDIA_ROOT}")
+print(f"  MEDIA_ROOT 존재: {os.path.exists(settings.MEDIA_ROOT)}")
+print()
+
+print("국제화:")
+print(f"  TIME_ZONE: {settings.TIME_ZONE}")
+print(f"  LANGUAGE_CODE: {settings.LANGUAGE_CODE}")
+print()
+
+print("설치된 앱:")
+for app in settings.INSTALLED_APPS:
+    print(f"  - {app}")
+print()
+
+print("="*80)
+print("설정 확인 완료!")
+print("="*80)