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/urls.py

@@ -0,0 +1,10 @@
+from django.urls import path
+from rest_framework_simplejwt.views import TokenRefreshView
+from . import views
+
+urlpatterns = [
+    path('admin/auth/login/', views.AdminLoginView.as_view(), name='admin_login'),
+    path('auth/refresh/', TokenRefreshView.as_view(), name='token_refresh'),
+    path('auth/me/', views.MeView.as_view(), name='auth_me'),
+    path('health/', views.HealthView.as_view(), name='health'),
+]