Reapply "Implement hidden_if_item_available_mode option (Z#23177008) (#4776)"

This reverts commit 5cd7959e86.

src/pretix/base/migrations/0276_item_hidden_if_item_available_mode.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.16 on 2025-01-23 11:27
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("pretixbase", "0275_alter_question_valid_number_max_and_more"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="item",
+            name="hidden_if_item_available_mode",
+            field=models.CharField(default="hide", max_length=16),
+        ),
+    ]