feat: add JWT auth foundation - /api/v1/ with admin login, refresh, me, health endpoints

- Add djangorestframework-simplejwt==5.3.1 to requirements-docker.txt
- Configure REST_FRAMEWORK with JWTAuthentication and SIMPLE_JWT settings
- Create admin_api Django app with AdminLoginView, MeView, HealthView
- Wire /api/v1/ routes without touching existing /api/ mobile endpoints
- Resolve pre-existing events migration conflict (0010_merge)
- Superuser admin created for initial authentication

admin_api/apps.py

@@ -0,0 +1,4 @@
+from django.apps import AppConfig
+class AdminApiConfig(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
+    name = 'admin_api'