Rewrite email parser using ImapEngine, harden processing loop

Replace webklex/php-imap with directorytree/imapengine in the ticket
email parser. ImapEngine is pure PHP over sockets.

Parser improvements:
- Wrap per-message processing in try/catch so one malformed email
  can't abort the run; failures are flagged and logged with UID
- Query unseen + unflagged so previously-failed (flagged) messages
  are no longer re-processed on every cron run
- Skip vacation/auto-responder emails (RFC 3834) to prevent mail
  loops with the ticket auto-reply
- Cap messages per run (50) and attachment size (15MB); inline
  images over 2MB are stored as attachments instead of base64-embedded
  in ticket details
- Atomic lock file creation
- preg_quote() the ticket prefix in subject matching
- Dedupe CC watchers and exclude the sender
- Map webklex 'tls' encryption setting to STARTTLS for compatibility

NDR/DSN parsing now walks MIME parts via the underlying
zbateson parser instead of relying on attachment extraction.

plugins/vendor/directorytree/imapengine/src/Address.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace DirectoryTree\ImapEngine;
+
+use DirectoryTree\ImapEngine\Support\Str;
+use Illuminate\Contracts\Support\Arrayable;
+use JsonSerializable;
+
+class Address implements Arrayable, JsonSerializable
+{
+    /**
+     * Constructor.
+     */
+    public function __construct(
+        protected string $email,
+        protected string $name,
+    ) {
+        $this->name = Str::decodeMimeHeader($this->name);
+    }
+
+    /**
+     * Get the address's email.
+     */
+    public function email(): string
+    {
+        return $this->email;
+    }
+
+    /**
+     * Get the address's name.
+     */
+    public function name(): string
+    {
+        return $this->name;
+    }
+
+    /**
+     * Get the array representation of the address.
+     */
+    public function toArray(): array
+    {
+        return [
+            'email' => $this->email,
+            'name' => $this->name,
+        ];
+    }
+
+    /**
+     * Get the JSON representation of the address.
+     */
+    public function jsonSerialize(): array
+    {
+        return $this->toArray();
+    }
+}