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/migrations/0005_userprofile_role.py

@@ -0,0 +1,26 @@
+# Generated by Django 4.2.29 on 2026-03-26 15:35
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("auth_app", "0004_userprofile"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="userprofile",
+            name="role",
+            field=models.CharField(
+                choices=[
+                    ("superadmin", "Super Admin"),
+                    ("admin", "Admin"),
+                    ("trainer", "Trainer"),
+                ],
+                default="trainer",
+                max_length=20,
+            ),
+        ),
+    ]