contact messages: bump corner ✉️ icon size to match its neighbors

frontend/src/assets/pagerite.css

@@ -413,6 +413,9 @@ body.editing #sidebar {
    and animates it (see contact-nudge by the trigger button). */
 .contact-icon {
   position: relative;
+  /* ✉️'s envelope glyph runs smaller than its emoji neighbors (📊, 🔐,
+     the flag) at the same font size; bump it to match their height. */
+  font-size: 1.25em;
 }
 
 .contact-icon.has-unread {