fix(mail): migrate filesystem helpers to fsUtils, update DKIM and mail APIs, harden SMTP client, and bump dependencies

ts/mail/core/classes.email.ts

@@ -613,17 +613,18 @@ export class Email {
     }
     
     // Add attachments
+    const smartFileFactory = plugins.smartfile.SmartFileFactory.nodeFs();
     for (const attachment of this.attachments) {
-      const smartAttachment = await plugins.smartfile.SmartFile.fromBuffer(
+      const smartAttachment = smartFileFactory.fromBuffer(
         attachment.filename,
         attachment.content
       );
-      
+
       // Set content type if available
       if (attachment.contentType) {
         (smartAttachment as any).contentType = attachment.contentType;
       }
-      
+
       smartmail.addAttachment(smartAttachment);
     }