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_views.py

@@ -1,7 +1,7 @@
 import pytest
 from taggit.models import Tag
 
-from apps.blog.models import ArticleIndexPage, ArticlePage
+from apps.blog.models import ArticleIndexPage, ArticlePage, Category
 from apps.blog.tests.factories import AuthorFactory
 from apps.comments.models import Comment
 
@@ -161,3 +161,75 @@ def test_article_index_renders_tag_filter_controls(client, home_page):
     html = resp.content.decode()
     assert resp.status_code == 200
     assert "/articles/?tag=tag-one" in html
+
+
+@pytest.mark.django_db
+def test_article_index_category_route_filters_articles(client, home_page):
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+    reviews = Category.objects.create(name="Reviews", slug="reviews")
+    tutorials = Category.objects.create(name="Tutorials", slug="tutorials")
+    review_article = ArticlePage(
+        title="Review A",
+        slug="review-a",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+        category=reviews,
+    )
+    tutorial_article = ArticlePage(
+        title="Tutorial A",
+        slug="tutorial-a",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+        category=tutorials,
+    )
+    index.add_child(instance=review_article)
+    review_article.save_revision().publish()
+    index.add_child(instance=tutorial_article)
+    tutorial_article.save_revision().publish()
+
+    resp = client.get("/articles/category/reviews/")
+    html = resp.content.decode()
+    assert resp.status_code == 200
+    assert "Review A" in html
+    assert "Tutorial A" not in html
+
+
+@pytest.mark.django_db
+def test_article_index_category_route_supports_tag_filter(client, home_page):
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    author = AuthorFactory()
+    reviews = Category.objects.create(name="Reviews", slug="reviews")
+    keep = ArticlePage(
+        title="Keep Me",
+        slug="keep-me",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+        category=reviews,
+    )
+    drop = ArticlePage(
+        title="Drop Me",
+        slug="drop-me",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+        category=reviews,
+    )
+    index.add_child(instance=keep)
+    keep.save_revision().publish()
+    index.add_child(instance=drop)
+    drop.save_revision().publish()
+    target_tag = Tag.objects.create(name="Python", slug="python")
+    keep.tags.add(target_tag)
+    keep.save_revision().publish()
+
+    resp = client.get("/articles/category/reviews/?tag=python")
+    html = resp.content.decode()
+    assert resp.status_code == 200
+    assert "Keep Me" in html
+    assert "Drop Me" not in html