fix(security): sanitize email rich body render path (#5212)

static/js/markdown.js

@@ -133,7 +133,7 @@ function _cleanAllowedHtmlOnce(htmlString) {
   return tpl.innerHTML;
 }
 
-function sanitizeAllowedHtml(html) {
+export function sanitizeAllowedHtml(html) {
   const raw = String(html == null ? '' : html);
   // Non-browser context (e.g. a future SSR/Node import): fail closed by
   // escaping rather than trusting the markup.
@@ -824,6 +824,7 @@ export function renderMermaid(container) {
 const markdownModule = {
   escapeHtml,
   mdToHtml,
+  sanitizeAllowedHtml,
   squashOutsideCode,
   renderContent,
   processWithThinking,