Add category taxonomy and navigation integration

Implements Issue #35 with category snippets, article category routing, category-aware templates, and category RSS feeds with tests.

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

apps/blog/tests/test_feeds_more.py

@@ -1,6 +1,8 @@
 import pytest
 
 from apps.blog.feeds import AllArticlesFeed
+from apps.blog.models import ArticleIndexPage, ArticlePage, Category
+from apps.blog.tests.factories import AuthorFactory
 
 
 @pytest.mark.django_db
@@ -16,3 +18,32 @@ def test_all_feed_methods(article_page):
 def test_tag_feed_not_found(client):
     resp = client.get("/feed/tag/does-not-exist/")
     assert resp.status_code == 404
+
+
+@pytest.mark.django_db
+def test_category_feed_endpoint(client, home_page):
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    category = Category.objects.create(name="Reviews", slug="reviews")
+    author = AuthorFactory()
+    article = ArticlePage(
+        title="Feed Review",
+        slug="feed-review",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>Body</p>")],
+        category=category,
+    )
+    index.add_child(instance=article)
+    article.save_revision().publish()
+
+    resp = client.get("/feed/category/reviews/")
+    assert resp.status_code == 200
+    assert resp["Content-Type"].startswith("application/rss+xml")
+    assert "Feed Review" in resp.content.decode()
+
+
+@pytest.mark.django_db
+def test_category_feed_not_found(client):
+    resp = client.get("/feed/category/does-not-exist/")
+    assert resp.status_code == 404