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 Unpublished pages are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/models.py

@@ -1,10 +1,24 @@
 from django.db import models
 from django.db.models import SET_NULL
+from modelcluster.fields import ParentalKey
+from modelcluster.models import ClusterableModel
+from wagtail.admin.panels import FieldPanel, InlinePanel, MultiFieldPanel
 from wagtail.contrib.settings.models import BaseSiteSetting, register_setting
+from wagtail.models import Orderable
+
+SOCIAL_ICON_CHOICES = [
+    ("twitter", "Twitter / X"),
+    ("github", "GitHub"),
+    ("rss", "RSS Feed"),
+    ("linkedin", "LinkedIn"),
+    ("youtube", "YouTube"),
+    ("mastodon", "Mastodon"),
+    ("bluesky", "Bluesky"),
+]
 
 
 @register_setting
-class SiteSettings(BaseSiteSetting):
+class SiteSettings(ClusterableModel, BaseSiteSetting):
     default_og_image = models.ForeignKey(
         "wagtailimages.Image",
         null=True,
@@ -19,3 +33,140 @@ class SiteSettings(BaseSiteSetting):
         on_delete=SET_NULL,
         related_name="+",
     )
+
+    # Branding
+    site_name = models.CharField(max_length=100, default="NO HYPE AI")
+    tagline = models.CharField(
+        max_length=200,
+        default="Honest AI tool reviews for developers.",
+    )
+    footer_description = models.TextField(
+        default="In-depth reviews and benchmarks of the latest AI coding tools.\nHonest analysis for developers.",
+        blank=True,
+    )
+    copyright_text = models.CharField(
+        max_length=200,
+        default="No Hype AI. All rights reserved.",
+    )
+
+    panels = [
+        MultiFieldPanel(
+            [
+                FieldPanel("site_name"),
+                FieldPanel("tagline"),
+                FieldPanel("footer_description"),
+                FieldPanel("copyright_text"),
+            ],
+            heading="Branding",
+        ),
+        MultiFieldPanel(
+            [
+                FieldPanel("default_og_image"),
+                FieldPanel("privacy_policy_page"),
+            ],
+            heading="SEO & Legal",
+        ),
+        InlinePanel("navigation_items", label="Navigation Menu Items"),
+        InlinePanel("social_links", label="Social Media Links"),
+    ]
+
+
+class NavigationMenuItem(Orderable):
+    settings = ParentalKey(
+        SiteSettings,
+        on_delete=models.CASCADE,
+        related_name="navigation_items",
+    )
+    link_page = models.ForeignKey(
+        "wagtailcore.Page",
+        null=True,
+        blank=True,
+        on_delete=SET_NULL,
+        related_name="+",
+        help_text="Link to an internal page. If unpublished, the link is hidden automatically.",
+    )
+    link_url = models.URLField(
+        blank=True,
+        default="",
+        help_text="External URL (used only when no page is selected).",
+    )
+    link_title = models.CharField(
+        max_length=100,
+        blank=True,
+        default="",
+        help_text="Override the display text. If blank, the page title is used.",
+    )
+    open_in_new_tab = models.BooleanField(default=False)
+    show_in_header = models.BooleanField(default=True)
+    show_in_footer = models.BooleanField(default=True)
+
+    panels = [
+        FieldPanel("link_page"),
+        FieldPanel("link_url"),
+        FieldPanel("link_title"),
+        FieldPanel("open_in_new_tab"),
+        FieldPanel("show_in_header"),
+        FieldPanel("show_in_footer"),
+    ]
+
+    @property
+    def title(self):
+        if self.link_title:
+            return self.link_title
+        if self.link_page:
+            return self.link_page.title
+        return ""
+
+    @property
+    def url(self):
+        if self.link_page:
+            return self.link_page.url
+        return self.link_url
+
+    @property
+    def is_live(self):
+        """Return False if linked to an unpublished/non-live page."""
+        if self.link_page_id:
+            return self.link_page.live
+        return bool(self.link_url)
+
+    class Meta(Orderable.Meta):
+        pass
+
+
+class SocialMediaLink(Orderable):
+    settings = ParentalKey(
+        SiteSettings,
+        on_delete=models.CASCADE,
+        related_name="social_links",
+    )
+    platform = models.CharField(
+        max_length=30,
+        choices=SOCIAL_ICON_CHOICES,
+    )
+    url = models.URLField()
+    label = models.CharField(
+        max_length=100,
+        blank=True,
+        default="",
+        help_text="Display label. If blank, the platform name is used.",
+    )
+
+    panels = [
+        FieldPanel("platform"),
+        FieldPanel("url"),
+        FieldPanel("label"),
+    ]
+
+    @property
+    def display_label(self):
+        if self.label:
+            return self.label
+        return dict(SOCIAL_ICON_CHOICES).get(self.platform, self.platform)
+
+    @property
+    def icon_template(self):
+        return f"components/icons/{self.platform}.html"
+
+    class Meta(Orderable.Meta):
+        pass