feat: implement comprehensive route-based email routing system

Replace legacy domain-rule based routing with flexible route-based system that supports:
- Multi-criteria matching (recipients, senders, IPs, authentication)
- Four action types (forward, process, deliver, reject)
- Moved DKIM signing to delivery phase for signature validity
- Connection pooling for efficient email forwarding
- Pattern caching for improved performance

This provides more granular control over email routing with priority-based matching and comprehensive test coverage.

ts/mail/routing/index.ts

@@ -1,5 +1,7 @@
 // Email routing components
 export * from './classes.domain.router.js';
 export * from './classes.email.config.js';
+export * from './classes.email.router.js';
 export * from './classes.unified.email.server.js';
-export * from './classes.dnsmanager.js';
+export * from './classes.dnsmanager.js';
+export * from './interfaces.js';