feat(comments): v2 — HTMX, Turnstile, reactions, design refresh

- Extract comment templates into reusable partials (_comment.html,
  _comment_form.html, _comment_list.html, _reply_form.html, etc.)
- Add HTMX progressive enhancement: inline form submission with
  partial responses, delta polling for live updates, form reset on
  success, success/moderation toast feedback
- Integrate Cloudflare Turnstile for invisible bot protection:
  server-side token validation with hostname check, fail-closed on
  errors/timeouts, feature-flagged via TURNSTILE_SECRET_KEY env var
- Auto-approve comments that pass Turnstile; keep manual approval
  as fallback when Turnstile is disabled (model default stays False)
- Add CommentReaction model with UniqueConstraint for session-based
  anonymous reactions (heart/thumbs-up), toggle support, separate
  rate-limit bucket (20/min)
- Add comment poll endpoint (GET /comments/poll/<id>/?after_id=N)
  for HTMX delta polling without duplicates
- Update CSP middleware to allow challenges.cloudflare.com in
  script-src, connect-src, and frame-src
- Self-host htmx.min.js (v2.0.4) to minimize CSP surface area
- Add django-htmx middleware and requests to dependencies
- Add Unapprove bulk action to Wagtail admin for moderation
- Extend PII purge command to anonymize reaction session_key
- Design refresh: neon glow avatars, solid hover shadows, gradient
  section header, cyan reply borders, grid-pattern empty state,
  neon-pink focus glow on form inputs
- Add turnstile_site_key to template context via context processor
- 18 new tests covering HTMX contracts, Turnstile success/failure/
  timeout/hostname-mismatch, polling deltas, reaction toggle/dedup/
  rate-limit, CSP headers, and PII purge extension

Closes #43

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

apps/comments/wagtail_hooks.py

@@ -41,6 +41,34 @@ class ApproveCommentBulkAction(SnippetBulkAction):
         ) % {"count": num_parent_objects}
 
 
+class UnapproveCommentBulkAction(SnippetBulkAction):
+    display_name = _("Unapprove")
+    action_type = "unapprove"
+    aria_label = _("Unapprove selected comments")
+    template_name = "comments/confirm_bulk_unapprove.html"
+    action_priority = 30
+    models = [Comment]
+
+    def check_perm(self, snippet):
+        if getattr(self, "can_change_items", None) is None:
+            self.can_change_items = self.request.user.has_perm(get_permission_name("change", self.model))
+        return self.can_change_items
+
+    @classmethod
+    def execute_action(cls, objects, **kwargs):
+        updated = kwargs["self"].model.objects.filter(pk__in=[obj.pk for obj in objects], is_approved=True).update(
+            is_approved=False
+        )
+        return updated, 0
+
+    def get_success_message(self, num_parent_objects, num_child_objects):
+        return ngettext(
+            "%(count)d comment unapproved.",
+            "%(count)d comments unapproved.",
+            num_parent_objects,
+        ) % {"count": num_parent_objects}
+
+
 class CommentViewSet(SnippetViewSet):
     model = Comment
     queryset = Comment.objects.all()
@@ -70,3 +98,4 @@ class CommentViewSet(SnippetViewSet):
 
 register_snippet(CommentViewSet)
 hooks.register("register_bulk_action", ApproveCommentBulkAction)
+hooks.register("register_bulk_action", UnapproveCommentBulkAction)