Fix image rendering in markdown comments

- markdown.js: add renderMarkdownComments() called on DOMContentLoaded to
  process [data-markdown] elements that were never being rendered on page load
- CSP: allow https: in img-src so external images in markdown aren't blocked

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/js/markdown.js

@@ -436,11 +436,24 @@ function processPlainTextComments() {
     });
 }
 
+/**
+ * Render all [data-markdown] comment elements that haven't been rendered yet
+ */
+function renderMarkdownComments() {
+    document.querySelectorAll('.comment-text[data-markdown]:not([data-rendered])').forEach(el => {
+        el.innerHTML = parseMarkdown(el.textContent);
+        el.dataset.rendered = '1';
+    });
+}
+
 // Run on page load
 document.addEventListener('DOMContentLoaded', function() {
+    renderMarkdownComments();
     processPlainTextComments();
 });
 
+window.renderMarkdownComments = renderMarkdownComments;
+
 // Expose for manual use
 window.autoLinkUrls = autoLinkUrls;
 window.processPlainTextComments = processPlainTextComments;