fix: Mailgun reply-to header and named 'to' recipient support

[deepshekhardas]

Summary

Fixes the Mailgun adapter to properly handle Reply-To header and adds support for named recipients in the 'to' field.

Changes

1. Fix h:Reply-To header - The header was missing => operator, causing Reply-To to be silently ignored
2. Add named 'to' recipients - Support ['email' => '...', 'name' => '...'] format matching cc/bcc
3. Fix from address format - RFC 5322 compliant "Name <email>" format

Related Issue

This addresses the P1 bug found in PR utopia-php#114 where the Mailgun h:Reply-To entry was a numeric-indexed value instead of a keyed header.

---

Summary by cubic

Fixes Mailgun Reply-To and named recipient handling. Adds MSG91 tracking metadata and passes SMS metadata through GEOSMS batches to improve traceability.

• New Features

  • SMS: added metadata support and propagation to adapters.
  • MSG91: accepts clientId, CRQID, and UUID; validates type, format, and length; ignores unknown keys; includes valid values in the request.
  • GEOSMS: forwards metadata to each routed adapter; when batching, appends -1, -2, etc. to CRQID/UUID to avoid duplicates, with validation.

• Bug Fixes

  • Mailgun: set h:Reply-To only when provided and with the correct key; support named to recipients; use RFC 5322-compliant from format.

^{Written for commit 2b9201c. Summary will update on new commits.}