feat: implement route-based email routing system

- Add core interfaces (IEmailRoute, IEmailMatch, IEmailAction, IEmailContext)
- Create EmailRouter class with comprehensive matching capabilities
- Support for recipient/sender patterns, IP/CIDR matching, auth checks
- Add content matching (headers, size, subject, attachments)
- Implement pattern caching for performance
- Update plan with completed steps

ts/mail/routing/interfaces.ts

@@ -1,5 +1,5 @@
 import type { Email } from '../core/classes.email.js';
-import type { IExtendedSmtpSession } from '../delivery/smtpserver/interfaces.js';
+import type { IExtendedSmtpSession } from './classes.unified.email.server.js';
 
 /**
  * Route configuration for email routing