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/models.py

@@ -3,11 +3,18 @@ from django.contrib.auth.models import User
 
 
 class UserProfile(models.Model):
+    ROLE_CHOICES = [
+        ('superadmin', 'Super Admin'),
+        ('admin', 'Admin'),
+        ('trainer', 'Trainer'),
+    ]
+    
     user = models.OneToOneField(User, on_delete=models.CASCADE, related_name='profile')
     club = models.ForeignKey('clubs.Club', on_delete=models.SET_NULL, null=True, blank=True, related_name='user_profiles')
+    role = models.CharField(max_length=20, choices=ROLE_CHOICES, default='trainer')
 
     def __str__(self):
-        return f"{self.user.username} Profile"
+        return f"{self.user.username} Profile ({self.get_role_display()})"
 
 
 class UserPreferences(models.Model):