fix: Use brighter yellow for email highlighting

Change highlight color from pale yellow (#fef08a) to bright highlighter yellow (#FFEB3B) for better visibility against the light yellow notes section background in emails.

The Material Design yellow provides strong contrast while remaining pleasant to read, matching the look of a real highlighter marker.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

server/api/notes/email/[sermonId].post.ts

@@ -49,7 +49,8 @@ export default defineEventHandler(async (event) => {
   // Email clients don't support <style> blocks well, so we need inline styles
   userNotes = userNotes
     // Convert <mark> to <span> with inline background color (email clients often don't support <mark>)
-    .replace(/<mark>/gi, '<span style="background-color: #fef08a; padding: 2px 4px; border-radius: 2px;">')
+    // Using bright highlighter yellow (#FFEB3B) that stands out against the light yellow notes background
+    .replace(/<mark>/gi, '<span style="background-color: #FFEB3B; padding: 2px 4px; border-radius: 2px;">')
     .replace(/<\/mark>/gi, '</span>')
     // Add inline styles to other elements
     .replace(/<strong>/gi, '<strong style="font-weight: 700;">')