feat: add threaded comments with polymorphic targets and slug-based routing

Introduce `load_comments` helper supporting polymorphic target types (post, project, bug) with nested parent-child threading. Refactor comment creation to use `target_type`/`target_uid` and `resolve_target_redirect` for correct redirects. Replace raw UID-based post/project routes with slug-aware resolution via `resolve_post`/`resolve_project` and `make_combined_slug`. Update SEO, sitemap, and FAB styling to use slugs and hardcoded red accent. Add reusable `_comment_section.html` template.

devplacepy/templates/project_detail.html

@@ -1,6 +1,7 @@
 {% extends "base.html" %}
 {% block extra_head %}
 <link rel="stylesheet" href="/static/css/projects.css">
+<link rel="stylesheet" href="/static/css/post.css">
 <style>
 .project-detail-page {
     max-width: 720px;
@@ -134,11 +135,15 @@
             </form>
             {% endif %}
             {% if is_owner %}
-            <form method="POST" action="/projects/delete/{{ project['uid'] }}" style="display:inline;">
+            <form method="POST" action="/projects/delete/{{ project['slug'] or project['uid'] }}" style="display:inline;">
                 <button type="submit" class="project-star-btn" onclick="return confirm('Delete this project?')">Delete</button>
             </form>
             {% endif %}
         </div>
     </article>
+
+    {% with target_uid=project['uid'], target_type="project" %}
+    {% include "_comment_section.html" %}
+    {% endwith %}
 </div>
 {% endblock %}