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/views.py

@@ -1,16 +1,25 @@
 from __future__ import annotations
 
+import logging
+from urllib.parse import urlencode
+
+import requests as http_requests
 from django.conf import settings
 from django.contrib import messages
 from django.core.cache import cache
 from django.core.exceptions import ValidationError
-from django.http import HttpResponse
+from django.db import IntegrityError
+from django.db.models import F, Prefetch
+from django.http import HttpResponse, JsonResponse
 from django.shortcuts import get_object_or_404, redirect, render
 from django.views import View
+from django.views.decorators.http import require_GET, require_POST
 
 from apps.blog.models import ArticlePage
 from apps.comments.forms import CommentForm
-from apps.comments.models import Comment
+from apps.comments.models import Comment, CommentReaction
+
+logger = logging.getLogger(__name__)
 
 
 def client_ip_from_request(request) -> str:
@@ -22,11 +31,53 @@ def client_ip_from_request(request) -> str:
     return remote_addr
 
 
+def _is_htmx(request) -> bool:
+    return request.headers.get("HX-Request") == "true"
+
+
+def _add_vary_header(response):
+    response["Vary"] = "HX-Request"
+    return response
+
+
+def _verify_turnstile(token: str, ip: str) -> bool:
+    secret = getattr(settings, "TURNSTILE_SECRET_KEY", "")
+    if not secret:
+        return False
+    try:
+        resp = http_requests.post(
+            "https://challenges.cloudflare.com/turnstile/v0/siteverify",
+            data={"secret": secret, "response": token, "remoteip": ip},
+            timeout=5,
+        )
+        result = resp.json()
+        if not result.get("success"):
+            return False
+        expected_hostname = getattr(settings, "TURNSTILE_EXPECTED_HOSTNAME", "")
+        if expected_hostname and result.get("hostname") != expected_hostname:
+            logger.warning("Turnstile hostname mismatch: %s", result.get("hostname"))
+            return False
+        return True
+    except Exception:
+        logger.exception("Turnstile verification failed")
+        return False
+
+
+def _turnstile_enabled() -> bool:
+    return bool(getattr(settings, "TURNSTILE_SECRET_KEY", ""))
+
+
 class CommentCreateView(View):
     def _render_article_with_errors(self, request, article, form):
+        if _is_htmx(request):
+            ctx = {"comment_form": form, "page": article}
+            ctx["turnstile_site_key"] = getattr(settings, "TURNSTILE_SITE_KEY", "")
+            resp = render(request, "comments/_comment_form.html", ctx, status=422)
+            return _add_vary_header(resp)
         context = article.get_context(request)
         context["page"] = article
         context["comment_form"] = form
+        context["turnstile_site_key"] = getattr(settings, "TURNSTILE_SITE_KEY", "")
         return render(request, "blog/article_page.html", context, status=200)
 
     def post(self, request):
@@ -45,9 +96,21 @@ class CommentCreateView(View):
 
         if form.is_valid():
             if form.cleaned_data.get("honeypot"):
+                if _is_htmx(request):
+                    return _add_vary_header(
+                        render(request, "comments/_comment_success.html", {"message": "Comment posted!"})
+                    )
                 return redirect(f"{article.url}?commented=1")
+
+            # Turnstile verification
+            turnstile_ok = False
+            if _turnstile_enabled():
+                token = request.POST.get("cf-turnstile-response", "")
+                turnstile_ok = _verify_turnstile(token, ip)
+
             comment = form.save(commit=False)
             comment.article = article
+            comment.is_approved = turnstile_ok
             parent_id = form.cleaned_data.get("parent_id")
             if parent_id:
                 comment.parent = Comment.objects.filter(pk=parent_id, article=article).first()
@@ -58,7 +121,97 @@ class CommentCreateView(View):
                 form.add_error(None, "Reply depth exceeds the allowed limit")
                 return self._render_article_with_errors(request, article, form)
             comment.save()
-            messages.success(request, "Your comment is awaiting moderation")
+
+            if _is_htmx(request):
+                if comment.is_approved:
+                    resp = render(request, "comments/_comment.html", {
+                        "comment": comment, "page": article,
+                        "turnstile_site_key": getattr(settings, "TURNSTILE_SITE_KEY", ""),
+                    })
+                else:
+                    resp = render(request, "comments/_comment_success.html", {
+                        "message": "Your comment has been posted and is awaiting moderation.",
+                    })
+                return _add_vary_header(resp)
+
+            messages.success(
+                request,
+                "Comment posted!" if comment.is_approved else "Your comment is awaiting moderation",
+            )
             return redirect(f"{article.url}?commented=1")
 
         return self._render_article_with_errors(request, article, form)
+
+
+@require_GET
+def comment_poll(request, article_id):
+    """Return comments newer than after_id for HTMX polling."""
+    article = get_object_or_404(ArticlePage, pk=article_id)
+    after_id = request.GET.get("after_id", "0")
+    try:
+        after_id = int(after_id)
+    except (ValueError, TypeError):
+        after_id = 0
+
+    approved_replies = Comment.objects.filter(is_approved=True).select_related("parent")
+    comments = (
+        article.comments.filter(is_approved=True, parent__isnull=True, id__gt=after_id)
+        .prefetch_related(Prefetch("replies", queryset=approved_replies))
+        .order_by("created_at", "id")
+    )
+
+    resp = render(request, "comments/_comment_list_inner.html", {
+        "approved_comments": comments,
+        "page": article,
+        "turnstile_site_key": getattr(settings, "TURNSTILE_SITE_KEY", ""),
+    })
+    return _add_vary_header(resp)
+
+
+@require_POST
+def comment_react(request, comment_id):
+    """Toggle a reaction on a comment."""
+    ip = client_ip_from_request(request)
+    key = f"reaction-rate:{ip}"
+    count = cache.get(key, 0)
+    rate_limit = getattr(settings, "REACTION_RATE_LIMIT_PER_MINUTE", 20)
+    if count >= rate_limit:
+        return HttpResponse(status=429)
+    cache.set(key, count + 1, timeout=60)
+
+    comment = get_object_or_404(Comment, pk=comment_id, is_approved=True)
+    reaction_type = request.POST.get("reaction_type", "heart")
+    if reaction_type not in ("heart", "plus_one"):
+        return HttpResponse(status=400)
+
+    if not request.session.session_key:
+        request.session.create()
+    session_key = request.session.session_key
+
+    try:
+        existing = CommentReaction.objects.filter(
+            comment=comment, reaction_type=reaction_type, session_key=session_key
+        ).first()
+        if existing:
+            existing.delete()
+        else:
+            CommentReaction.objects.create(
+                comment=comment, reaction_type=reaction_type, session_key=session_key
+            )
+    except IntegrityError:
+        pass
+
+    counts = {}
+    for rt in ("heart", "plus_one"):
+        counts[rt] = comment.reactions.filter(reaction_type=rt).count()
+    user_reacted = set(
+        comment.reactions.filter(session_key=session_key).values_list("reaction_type", flat=True)
+    )
+
+    if _is_htmx(request):
+        resp = render(request, "comments/_reactions.html", {
+            "comment": comment, "counts": counts, "user_reacted": user_reacted,
+        })
+        return _add_vary_header(resp)
+
+    return JsonResponse({"counts": counts, "user_reacted": list(user_reacted)})