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/permissions.py

@@ -0,0 +1,25 @@
+from rest_framework import permissions
+
+class IsSuperAdmin(permissions.BasePermission):
+    def has_permission(self, request, view):
+        return (
+            request.user.is_authenticated and 
+            hasattr(request.user, 'profile') and 
+            request.user.profile.role == 'superadmin'
+        )
+
+class IsAdminOrSuperAdmin(permissions.BasePermission):
+    def has_permission(self, request, view):
+        if not request.user.is_authenticated:
+            return False
+        if not hasattr(request.user, 'profile'):
+            return False
+        return request.user.profile.role in ['admin', 'superadmin']
+
+class HasUserManagementAccess(permissions.BasePermission):
+    def has_permission(self, request, view):
+        if not request.user.is_authenticated:
+            return False
+        if not hasattr(request.user, 'profile'):
+            return False
+        return request.user.profile.role == 'superadmin'