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/core/templatetags/core_tags.py

@@ -4,7 +4,7 @@ from django import template
 from django.utils.safestring import mark_safe
 from wagtail.models import Site
 
-from apps.blog.models import TagMetadata
+from apps.blog.models import ArticleIndexPage, TagMetadata
 from apps.core.models import SiteSettings
 from apps.legal.models import LegalPage
 
@@ -46,6 +46,30 @@ def get_social_links(context):
     return list(settings.social_links.all())
 
 
+@register.simple_tag(takes_context=True)
+def get_categories_nav(context):
+    request = context.get("request")
+    if not request:
+        return []
+    site = Site.find_for_request(request) if request else None
+    index_qs = ArticleIndexPage.objects.live().public()
+    if site:
+        index_qs = index_qs.in_site(site)
+    index_page = index_qs.first()
+    if not index_page:
+        return []
+    categories = index_page.get_listing_context(request, active_category=None)["available_categories"].filter(show_in_nav=True)
+    return [
+        {
+            "name": category.name,
+            "slug": category.slug,
+            "url": index_page.get_category_url(category),
+            "article_count": index_page.get_articles().filter(category=category).count(),
+        }
+        for category in categories
+    ]
+
+
 @register.simple_tag
 @register.filter
 def get_tag_css(tag):

apps/core/tests/test_tags.py

@@ -1,5 +1,7 @@
 import pytest
 
+from apps.blog.models import ArticleIndexPage, ArticlePage, Category
+from apps.blog.tests.factories import AuthorFactory
 from apps.legal.models import LegalIndexPage, LegalPage
 
 
@@ -13,3 +15,25 @@ def test_get_legal_pages_tag(client, home_page):
 
     resp = client.get("/")
     assert resp.status_code == 200
+
+
+@pytest.mark.django_db
+def test_categories_nav_tag_renders_category_link(client, home_page):
+    index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=index)
+    category = Category.objects.create(name="Reviews", slug="reviews", show_in_nav=True)
+    author = AuthorFactory()
+    article = ArticlePage(
+        title="R1",
+        slug="r1",
+        author=author,
+        summary="summary",
+        body=[("rich_text", "<p>body</p>")],
+        category=category,
+    )
+    index.add_child(instance=article)
+    article.save_revision().publish()
+
+    resp = client.get("/")
+    assert resp.status_code == 200
+    assert "/articles/category/reviews/" in resp.content.decode()