Switch to using triggers

Still outstanding:

* IPAddress and IPRange triggers
* Triggers for VRF changes on Prefix
* Triggers for changing to "container" on Prefix
* Rework logic for saving on all models

netbox/ipam/migrations/0085_alter_prefix_parent.py

@@ -0,0 +1,25 @@
+# Generated by Django 5.2.5 on 2025-11-25 03:53
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('ipam', '0084_prefix_ipam_prefix_delete_prefix_ipam_prefix_insert'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='prefix',
+            name='parent',
+            field=models.ForeignKey(
+                blank=True,
+                null=True,
+                on_delete=django.db.models.deletion.DO_NOTHING,
+                related_name='children',
+                to='ipam.prefix',
+            ),
+        ),
+    ]