feat(rust): scaffold Rust workspace and fix TypeScript build errors

- Add @git.zone/tsrust with linux_amd64/linux_arm64 cross-compilation
- Scaffold Rust workspace with 5 crates: mailer-core, mailer-smtp, mailer-security, mailer-napi, mailer-bin
- Fix all TypeScript compilation errors for upgraded dependencies (smartfile v13, mailauth v4.13, smartproxy v23)
- Replace smartfile.fs/memory with @push.rocks/smartfs throughout codebase
- Fix .ts import extensions to .js for NodeNext module resolution
- Update DKIMSignOptions usage to match mailauth v4.13 API
- Add MTA error classes with permissive signatures for legacy SMTP client
- Replace removed DcRouter/StorageManager/deliverability imports with local interfaces

ts/mail/delivery/smtpclient/command-handler.ts

@@ -4,20 +4,20 @@
  */
 
 import { EventEmitter } from 'node:events';
-import { SMTP_COMMANDS, SMTP_CODES, LINE_ENDINGS } from './constants.ts';
+import { SMTP_COMMANDS, SMTP_CODES, LINE_ENDINGS } from './constants.js';
 import type { 
   ISmtpConnection, 
   ISmtpResponse, 
   ISmtpClientOptions,
   ISmtpCapabilities 
-} from './interfaces.ts';
+} from './interfaces.js';
 import { 
   parseSmtpResponse, 
   parseEhloResponse, 
   formatCommand,
   isSuccessCode 
-} from './utils/helpers.ts';
-import { logCommand, logDebug } from './utils/logging.ts';
+} from './utils/helpers.js';
+import { logCommand, logDebug } from './utils/logging.js';
 
 export class CommandHandler extends EventEmitter {
   private options: ISmtpClientOptions;