feat: implement user management system

- Add role field to UserProfile (superadmin/admin/trainer)
- Add role-based permission classes
- Create UserManagementViewSet with CRUD and password change
- Add API types and components for user management
- Create users management page in settings
- Only superadmins can manage users

backend/auth_app/urls.py

@@ -0,0 +1,15 @@
+from django.urls import path, include
+from rest_framework.routers import DefaultRouter
+from . import views
+
+router = DefaultRouter()
+router.register(r'users', views.UserManagementViewSet, basename='usermanagement')
+
+urlpatterns = [
+    path('login/', views.login, name='login'),
+    path('register/', views.register, name='register'),
+    path('refresh/', views.refresh_token, name='refresh'),
+    path('me/', views.me, name='me'),
+    path('preferences/', views.user_preferences, name='preferences'),
+    path('', include(router.urls)),
+]