feat: improve Wagtail admin editor experience for articles

- Add published_date field to ArticlePage with auto-populate from
  first_published_at on first publish, plus data migration backfill
- Surface go_live_at/expire_at scheduling fields in editor panels
- Reorganise ArticlePage editor with TabbedInterface (Content,
  Metadata, Publishing, SEO tabs)
- Add Articles PageListingViewSet to admin menu with custom columns
  (author, category, published date, status) and category/author filters
- Add Articles summary dashboard panel showing drafts, scheduled,
  and recently published articles
- Update all front-end queries and RSS feeds to use published_date
- Add 10 unit tests and 4 E2E tests for new admin features

Closes #39

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

apps/blog/tests/factories.py

@@ -37,6 +37,7 @@ class ArticlePageFactory(wagtail_factories.PageFactory):
     summary = "Summary"
     body = [("rich_text", "<p>Hello world</p>")]
     first_published_at = factory.LazyFunction(timezone.now)
+    published_date = factory.LazyFunction(timezone.now)
 
 
 class LegalIndexPageFactory(wagtail_factories.PageFactory):

apps/blog/tests/test_admin_experience.py

@@ -0,0 +1,232 @@
+import pytest
+from django.test import override_settings
+from django.utils import timezone
+
+from apps.blog.models import ArticleIndexPage, ArticlePage, Category
+from apps.blog.tests.factories import AuthorFactory
+
+
+@pytest.mark.django_db
+def test_published_date_auto_set_on_first_publish(home_page):
+    """published_date should be auto-populated from first_published_at on first publish."""
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+    article = ArticlePage(
+        title="Auto Date",
+        slug="auto-date",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+    )
+    index.add_child(instance=article)
+    article.save_revision().publish()
+    article.refresh_from_db()
+    assert article.published_date is not None
+    assert article.published_date == article.first_published_at
+
+
+@pytest.mark.django_db
+def test_published_date_preserved_when_explicitly_set(home_page):
+    """An explicitly set published_date should not be overwritten on save."""
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+    custom_date = timezone.now() - timezone.timedelta(days=30)
+    article = ArticlePage(
+        title="Custom Date",
+        slug="custom-date",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+        published_date=custom_date,
+    )
+    index.add_child(instance=article)
+    article.save_revision().publish()
+    article.refresh_from_db()
+    assert article.published_date == custom_date
+
+
+@pytest.mark.django_db
+def test_homepage_orders_articles_by_published_date(home_page):
+    """HomePage context should list articles ordered by -published_date."""
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+
+    older = ArticlePage(
+        title="Older",
+        slug="older",
+        author=author,
+        summary="s",
+        body=[("rich_text", "<p>body</p>")],
+        published_date=timezone.now() - timezone.timedelta(days=10),
+    )
+    index.add_child(instance=older)
+    older.save_revision().publish()
+
+    newer = ArticlePage(
+        title="Newer",
+        slug="newer",
+        author=author,
+        summary="s",
+        body=[("rich_text", "<p>body</p>")],
+        published_date=timezone.now(),
+    )
+    index.add_child(instance=newer)
+    newer.save_revision().publish()
+
+    ctx = home_page.get_context(type("Req", (), {"GET": {}})())
+    titles = [a.title for a in ctx["latest_articles"]]
+    assert titles.index("Newer") < titles.index("Older")
+
+
+@pytest.mark.django_db
+def test_article_index_orders_by_published_date(home_page, rf):
+    """ArticleIndexPage.get_articles should order by -published_date."""
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+
+    old = ArticlePage(
+        title="Old",
+        slug="old",
+        author=author,
+        summary="s",
+        body=[("rich_text", "<p>b</p>")],
+        published_date=timezone.now() - timezone.timedelta(days=5),
+    )
+    index.add_child(instance=old)
+    old.save_revision().publish()
+
+    new = ArticlePage(
+        title="New",
+        slug="new",
+        author=author,
+        summary="s",
+        body=[("rich_text", "<p>b</p>")],
+        published_date=timezone.now(),
+    )
+    index.add_child(instance=new)
+    new.save_revision().publish()
+
+    articles = list(index.get_articles())
+    assert articles[0].title == "New"
+    assert articles[1].title == "Old"
+
+
+@pytest.mark.django_db
+def test_feed_uses_published_date(article_page):
+    """RSS feed item_pubdate should use published_date."""
+    from apps.blog.feeds import AllArticlesFeed
+
+    feed = AllArticlesFeed()
+    assert feed.item_pubdate(article_page) == article_page.published_date
+
+
+@pytest.mark.django_db
+@override_settings(ALLOWED_HOSTS=["testserver", "localhost", "127.0.0.1"])
+def test_articles_listing_viewset_loads(client, django_user_model, home_page):
+    """The Articles PageListingViewSet index page should load."""
+    admin = django_user_model.objects.create_superuser(
+        username="admin", email="admin@example.com", password="admin-pass"
+    )
+    client.force_login(admin)
+    response = client.get("/cms/articles/")
+    assert response.status_code == 200
+
+
+@pytest.mark.django_db
+@override_settings(ALLOWED_HOSTS=["testserver", "localhost", "127.0.0.1"])
+def test_articles_listing_shows_articles(client, django_user_model, home_page):
+    """The Articles listing should show existing articles."""
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+    article = ArticlePage(
+        title="Listed Article",
+        slug="listed-article",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+    )
+    index.add_child(instance=article)
+    article.save_revision().publish()
+
+    admin = django_user_model.objects.create_superuser(
+        username="admin", email="admin@example.com", password="admin-pass"
+    )
+    client.force_login(admin)
+    response = client.get("/cms/articles/")
+    assert response.status_code == 200
+    assert "Listed Article" in response.content.decode()
+
+
+@pytest.mark.django_db
+@override_settings(ALLOWED_HOSTS=["testserver", "localhost", "127.0.0.1"])
+def test_dashboard_panel_renders(client, django_user_model, home_page):
+    """The Wagtail admin dashboard should include the articles summary panel."""
+    admin = django_user_model.objects.create_superuser(
+        username="admin", email="admin@example.com", password="admin-pass"
+    )
+    client.force_login(admin)
+    response = client.get("/cms/")
+    assert response.status_code == 200
+    content = response.content.decode()
+    assert "Articles overview" in content
+
+
+@pytest.mark.django_db
+@override_settings(ALLOWED_HOSTS=["testserver", "localhost", "127.0.0.1"])
+def test_dashboard_panel_shows_drafts(client, django_user_model, home_page):
+    """Dashboard panel should list draft articles."""
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+    draft = ArticlePage(
+        title="My Draft Post",
+        slug="draft-post",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+    )
+    index.add_child(instance=draft)
+    draft.save_revision()  # save revision but don't publish
+
+    admin = django_user_model.objects.create_superuser(
+        username="admin", email="admin@example.com", password="admin-pass"
+    )
+    client.force_login(admin)
+    response = client.get("/cms/")
+    content = response.content.decode()
+    assert "My Draft Post" in content
+
+
+@pytest.mark.django_db
+@override_settings(ALLOWED_HOSTS=["testserver", "localhost", "127.0.0.1"])
+def test_article_edit_page_has_tabbed_interface(client, django_user_model, home_page):
+    """ArticlePage editor should have tabbed panels (Content, Metadata, Publishing, SEO)."""
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+    article = ArticlePage(
+        title="Tabbed",
+        slug="tabbed",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+    )
+    index.add_child(instance=article)
+    article.save_revision().publish()
+
+    admin = django_user_model.objects.create_superuser(
+        username="admin", email="admin@example.com", password="admin-pass"
+    )
+    client.force_login(admin)
+    response = client.get(f"/cms/pages/{article.pk}/edit/")
+    content = response.content.decode()
+    assert response.status_code == 200
+    assert "Content" in content
+    assert "Metadata" in content
+    assert "Publishing" in content
+    assert "SEO" in content