fix: remove problematic mailgun.js/Types import

- Remove unused MailgunMessageData type import
- Remove type annotations for messageData
- Resolves TypeScript compilation error in email-worker

The mailgun.js package doesn't properly expose Types module,
and the type annotation wasn't necessary since mailgunClient
is already typed as any.

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

email-worker/src/lib/mailgunService.ts

@@ -1,7 +1,6 @@
 import formData from 'form-data';
 import Mailgun from 'mailgun.js';
 import { createLogger } from './logger';
-import { MailgunMessageData } from 'mailgun.js/Types';
 
 const log = createLogger("email:mailgun");
 
@@ -47,14 +46,13 @@ export async function sendEmail(message: EmailMessage): Promise<boolean> {
         const client = getMailgunClient();
         const domain = process.env.MAILGUN_DOMAIN || 'rezije.app';
 
-        const messageData:MailgunMessageData = {
+        const messageData = {
             from: 'rezije.app <noreply@rezije.app>',
             to: message.to,
             subject: message.subject,
             html: message.html,
             "v:locationID": "12345" // testing custom variable - webhook should pick this up
-         } as MailgunMessageData;
-
+         };
 
         log(`Sending email to ${message.to}: ${message.subject}`);