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/classes.email.router.ts

@@ -50,6 +50,14 @@ export class EmailRouter extends EventEmitter {
     this.emit('routesUpdated', this.routes);
   }
   
+  /**
+   * Set routes (alias for updateRoutes)
+   * @param routes New routes
+   */
+  public setRoutes(routes: IEmailRoute[]): void {
+    this.updateRoutes(routes);
+  }
+  
   /**
    * Clear the pattern cache
    */