fix: address review feedback — URLField→CharField, safe reverse migration

- Change SocialMediaLink.url and NavigationMenuItem.link_url from
  URLField to CharField(max_length=500) to support internal paths
  like /feed/ that fail URLField validation
- Replace destructive reverse_seed (deleted ALL rows) with
  RunPython.noop to prevent data loss on rollback

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

apps/core/migrations/0003_seed_navigation_data.py

@@ -93,13 +93,6 @@ def seed_navigation_data(apps, schema_editor):
             )
 
 
-def reverse_seed(apps, schema_editor):
-    NavigationMenuItem = apps.get_model("core", "NavigationMenuItem")
-    SocialMediaLink = apps.get_model("core", "SocialMediaLink")
-    NavigationMenuItem.objects.all().delete()
-    SocialMediaLink.objects.all().delete()
-
-
 class Migration(migrations.Migration):
 
     dependencies = [
@@ -108,5 +101,5 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
-        migrations.RunPython(seed_navigation_data, reverse_seed),
+        migrations.RunPython(seed_navigation_data, migrations.RunPython.noop),
     ]

apps/core/migrations/0004_alter_navigationmenuitem_link_url_and_more.py

@@ -0,0 +1,23 @@
+# Generated by Django 5.2.11 on 2026-03-02 19:35
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0003_seed_navigation_data'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='navigationmenuitem',
+            name='link_url',
+            field=models.CharField(blank=True, default='', help_text='URL or path (used only when no page is selected).', max_length=500),
+        ),
+        migrations.AlterField(
+            model_name='socialmedialink',
+            name='url',
+            field=models.CharField(help_text='URL or path (e.g. https://twitter.com/… or /feed/).', max_length=500),
+        ),
+    ]