Fix admin message auto-dismiss and Category plural label

Admin messages now auto-clear after 8 seconds via the w-messages
Stimulus controller's autoClear value, preventing message pile-up.
Category model gains verbose_name_plural so Wagtail shows "Categories"
instead of "Categorys" in the snippets menu.

Closes #62

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/blog/migrations/0005_fix_category_verbose_name_plural.py

@@ -0,0 +1,17 @@
+# Generated by Django 5.2.12 on 2026-03-19 00:10
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('blog', '0004_backfill_published_date'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='category',
+            options={'ordering': ['sort_order', 'name'], 'verbose_name_plural': 'categories'},
+        ),
+    ]

apps/blog/models.py

@@ -168,6 +168,7 @@ class Category(models.Model):
 
     class Meta:
         ordering = ["sort_order", "name"]
+        verbose_name_plural = "categories"
 
     def __str__(self):
         return self.name

apps/blog/tests/test_admin_experience.py

@@ -386,6 +386,31 @@ def test_article_save_autogenerates_summary_when_missing(article_index):
     assert article.summary == "This should become the summary text."
 
 
+@pytest.mark.django_db
+def test_category_verbose_name_plural():
+    """Category Meta should define verbose_name_plural as 'categories'."""
+    assert Category._meta.verbose_name_plural == "categories"
+
+
+@pytest.mark.django_db
+@override_settings(ALLOWED_HOSTS=["testserver", "localhost", "127.0.0.1"])
+def test_snippet_category_listing_shows_categories(client, django_user_model):
+    """Categories created in the database should appear in the Snippets listing."""
+    Category.objects.create(name="Reviews", slug="reviews")
+    Category.objects.create(name="Tutorials", slug="tutorials")
+
+    admin = django_user_model.objects.create_superuser(
+        username="admin-cat", email="admin-cat@example.com", password="admin-pass"
+    )
+    client.force_login(admin)
+    response = client.get("/cms/snippets/blog/category/")
+    content = response.content.decode()
+
+    assert response.status_code == 200
+    assert "Reviews" in content
+    assert "Tutorials" in content
+
+
 @pytest.mark.django_db
 def test_article_page_omits_admin_messages_on_frontend(article_page, rf):
     """Frontend templates should not render admin session messages."""