feat: replace hardcoded navigation with CMS-managed models

Replace static nav/footer links with Wagtail-managed NavigationMenuItem
and SocialMediaLink orderables on SiteSettings. Unpublished pages are
automatically excluded from rendering, fixing the dead-link problem.

- Extend SiteSettings with site_name, tagline, footer_description,
  copyright_text branding fields
- Add NavigationMenuItem orderable (link_page/link_url, show_in_header,
  show_in_footer, sort_order) with automatic live-page filtering
- Add SocialMediaLink orderable with platform icon templates
- New template tags: get_nav_items, get_social_links
- Update nav.html and footer.html to render from CMS data
- Data migration seeds existing hardcoded values for zero-change deploy
- Update seed_e2e_content command for test/dev environments
- 18 new tests covering models, template tags, and rendered output

Closes #32

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

apps/core/tests/test_navigation.py

@@ -0,0 +1,191 @@
+import pytest
+from wagtail.models import Site
+
+from apps.blog.models import AboutPage, ArticleIndexPage
+from apps.core.models import NavigationMenuItem, SiteSettings, SocialMediaLink
+
+
+@pytest.fixture
+def site_with_nav(home_page):
+    """Create SiteSettings with nav items and social links for testing."""
+    site = Site.objects.get(is_default_site=True)
+    settings, _ = SiteSettings.objects.get_or_create(site=site)
+
+    # Clear any items seeded by the data migration
+    settings.navigation_items.all().delete()
+    settings.social_links.all().delete()
+
+    # Create article index and about page
+    article_index = ArticleIndexPage(title="Articles", slug="articles")
+    home_page.add_child(instance=article_index)
+    article_index.save_revision().publish()
+
+    about = AboutPage(
+        title="About",
+        slug="about",
+        mission_statement="Test mission",
+        body="<p>About page</p>",
+    )
+    home_page.add_child(instance=about)
+    about.save_revision().publish()
+
+    # Create nav items
+    NavigationMenuItem.objects.create(
+        settings=settings,
+        link_page=home_page,
+        link_title="Home",
+        show_in_header=True,
+        show_in_footer=True,
+        sort_order=0,
+    )
+    NavigationMenuItem.objects.create(
+        settings=settings,
+        link_page=article_index,
+        link_title="Articles",
+        show_in_header=True,
+        show_in_footer=True,
+        sort_order=1,
+    )
+    NavigationMenuItem.objects.create(
+        settings=settings,
+        link_page=about,
+        link_title="About",
+        show_in_header=True,
+        show_in_footer=False,
+        sort_order=2,
+    )
+
+    # Social links
+    SocialMediaLink.objects.create(
+        settings=settings,
+        platform="twitter",
+        url="https://twitter.com/nohypeai",
+        label="Twitter (X)",
+        sort_order=0,
+    )
+    SocialMediaLink.objects.create(
+        settings=settings,
+        platform="rss",
+        url="/feed/",
+        label="RSS Feed",
+        sort_order=1,
+    )
+
+    return settings
+
+
+@pytest.mark.django_db
+class TestNavigationMenuItem:
+    def test_live_page_is_rendered(self, site_with_nav):
+        items = [i for i in site_with_nav.navigation_items.all() if i.is_live]
+        assert len(items) == 3
+
+    def test_unpublished_page_excluded(self, site_with_nav):
+        about_item = site_with_nav.navigation_items.get(link_title="About")
+        about_item.link_page.unpublish()
+        items = [i for i in site_with_nav.navigation_items.all() if i.is_live]
+        assert len(items) == 2
+        assert all(i.link_title != "About" for i in items)
+
+    def test_external_url_item(self, site_with_nav):
+        NavigationMenuItem.objects.create(
+            settings=site_with_nav,
+            link_url="https://example.com",
+            link_title="External",
+            sort_order=10,
+        )
+        item = site_with_nav.navigation_items.get(link_title="External")
+        assert item.is_live is True
+        assert item.url == "https://example.com"
+        assert item.title == "External"
+
+    def test_title_falls_back_to_page_title(self, site_with_nav):
+        item = site_with_nav.navigation_items.get(sort_order=0)
+        item.link_title = ""
+        item.save()
+        assert item.title == item.link_page.title
+
+    def test_header_footer_filtering(self, site_with_nav):
+        header_items = site_with_nav.navigation_items.filter(show_in_header=True)
+        footer_items = site_with_nav.navigation_items.filter(show_in_footer=True)
+        assert header_items.count() == 3
+        assert footer_items.count() == 2  # About excluded from footer
+
+    def test_sort_order_respected(self, site_with_nav):
+        items = list(site_with_nav.navigation_items.all().order_by("sort_order"))
+        assert [i.link_title for i in items] == ["Home", "Articles", "About"]
+
+
+@pytest.mark.django_db
+class TestSocialMediaLink:
+    def test_display_label_from_field(self, site_with_nav):
+        link = site_with_nav.social_links.get(platform="twitter")
+        assert link.display_label == "Twitter (X)"
+
+    def test_display_label_fallback(self, site_with_nav):
+        link = site_with_nav.social_links.get(platform="twitter")
+        link.label = ""
+        assert link.display_label == "Twitter / X"
+
+    def test_icon_template_path(self, site_with_nav):
+        link = site_with_nav.social_links.get(platform="rss")
+        assert link.icon_template == "components/icons/rss.html"
+
+    def test_ordering(self, site_with_nav):
+        links = list(site_with_nav.social_links.all().order_by("sort_order"))
+        assert [link.platform for link in links] == ["twitter", "rss"]
+
+
+@pytest.mark.django_db
+class TestSiteSettingsDefaults:
+    def test_default_site_name(self, home_page):
+        site = Site.objects.get(is_default_site=True)
+        settings, _ = SiteSettings.objects.get_or_create(site=site)
+        assert settings.site_name == "NO HYPE AI"
+
+    def test_default_copyright(self, home_page):
+        site = Site.objects.get(is_default_site=True)
+        settings, _ = SiteSettings.objects.get_or_create(site=site)
+        assert settings.copyright_text == "No Hype AI. All rights reserved."
+
+    def test_default_tagline(self, home_page):
+        site = Site.objects.get(is_default_site=True)
+        settings, _ = SiteSettings.objects.get_or_create(site=site)
+        assert settings.tagline == "Honest AI tool reviews for developers."
+
+
+@pytest.mark.django_db
+class TestNavRendering:
+    def test_header_shows_nav_items(self, client, site_with_nav):
+        resp = client.get("/")
+        content = resp.content.decode()
+        assert "Home" in content
+        assert "Articles" in content
+        assert "About" in content
+
+    def test_unpublished_page_not_in_header(self, client, site_with_nav):
+        about_item = site_with_nav.navigation_items.get(link_title="About")
+        about_item.link_page.unpublish()
+        resp = client.get("/")
+        content = resp.content.decode()
+        # About should not appear as a nav link (but might appear elsewhere on page)
+        assert 'href="/about/"' not in content
+
+    def test_footer_shows_nav_items(self, client, site_with_nav):
+        resp = client.get("/")
+        content = resp.content.decode()
+        # Footer should have social links
+        assert "Twitter (X)" in content
+        assert "RSS Feed" in content
+
+    def test_footer_shows_branding(self, client, site_with_nav):
+        site_with_nav.site_name = "TEST SITE"
+        site_with_nav.save()
+        resp = client.get("/")
+        content = resp.content.decode()
+        assert "TEST SITE" in content
+
+    def test_footer_shows_copyright(self, client, site_with_nav):
+        resp = client.get("/")
+        content = resp.content.decode()
+        assert "No Hype AI. All rights reserved." in content