Email reminder bell: re-evaluate visibility live on settings change

The bell is already gated on settings.reminder_channel === 'email', but
the check only ran at email-library init — so switching the reminder
channel in Settings didn't update the bell until you reopened Email.

- Settings/Reminders channel-change handler now dispatches
  odysseus-reminder-channel-changed { channel } after saving.
- emailLibrary listens for it and re-runs _syncEmailReminderBellVisibility
  with the new channel value.

static/js/emailLibrary.js

@@ -321,6 +321,12 @@ async function _loadEmailReminderBellVisibility() {
     _syncEmailReminderBellVisibility(false);
   }
 }
+// Live-update the bell when the reminder channel changes in Settings,
+// so the user doesn't have to reopen Email to see the change apply.
+window.addEventListener('odysseus-reminder-channel-changed', (e) => {
+  const ch = e?.detail?.channel;
+  _syncEmailReminderBellVisibility(ch === 'email');
+});
 
 function _readCssPx(name) {
   const v = getComputedStyle(document.documentElement).getPropertyValue(name);