audio/baresip: Update 4.1.0 => 4.2.0, flavorize, take maintainership

Changelog:
https://github.com/baresip/baresip/releases/tag/v4.2.0

Improve port:

• Add JACK audio backend option.
• Fix Gstreamer audio backend.
• Introduce flavors:
  • nox11 - minimal console-only build for voice calls;
  • default - full build with X11 and video support.
• Replace BUILD_DEPENDS+RUN_DEPENDS from audio/re to LIB_DEPENDS.
• Sort PORTDOCS.
• Small formatting improvements.

PR: 290307
Approved by: Herbert J. Skuhra <herbert@gojira.at> (former maintainer)
Co-authored-by: Vladimir Druzenko <vvd@FreeBSD.org>
MFH: 2025Q4

(cherry picked from commit c76e8bd1807e910961ae276f6f5d0227f12cdb7b)