Release Jarl under the MIT License

LICENSE is installed with the docs, included in make dist, and becomes
the Debian package's copyright file together with the bundled Cinzel
font's OFL.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -143,6 +143,11 @@ Version 0.1.0, the first release. It is feature-complete for one server's
 configuration. DNSSEC signing and managing several servers are not handled
 yet ([concepts.md](docs/concepts.md#what-jarl-deliberately-doesnt-do-yet)).
 
+## License
+
+Jarl is released under the [MIT License](LICENSE). The bundled Cinzel font
+is under the SIL Open Font License 1.1 (below).
+
 ## Credits
 
 The "Jarl" name in the web UI's header uses [Cinzel](https://github.com/NDISCOVER/Cinzel) Bold