Improve email loading performance and fix UI issues

- Fixed refresh button icon not displaying (changed from icon prop to v-icon element)
- Reduced default email limit from 50 to 20 to improve loading speed
- Optimized cached email loading to only load most recent emails (up to limit)
- Fixed CommonJS require error in email-utils.ts (changed to ES module import)
- Added sorting to cached files to ensure newest emails are loaded first

This should significantly improve email loading performance from 578 cached files down to max 20

server/utils/email-utils.ts

@@ -1,6 +1,6 @@
 import { simpleParser } from 'mailparser';
 import type { ParsedMail } from 'mailparser';
-const Imap = require('imap');
+import Imap from 'imap';
 
 export type { ParsedMail };