Point links at git.coffeylabs.org after the move from GitHub

GitHub took the organisation's repos and GHCR offline on 2026-09-20. Repo,
release, raw-file and clone links now go to Gitea at git.coffeylabs.org,
container images to registry.coffeylabs.org, and GitLab-style /-/blob paths
to Gitea's /src/branch form. Go module paths are identifiers and stay as
they are; links to GitHub issues and pull requests are left as history.

CONTRIBUTING.md

@@ -17,7 +17,7 @@ By participating in this project you agree to abide by the [Code of Conduct](COD
 
 ### Reporting Bugs
 
-Search [existing issues](https://github.com/Coffey-Labs/cairnobs/issues) first. When filing a bug, include:
+Search [existing issues](https://git.coffeylabs.org/coffey-labs/cairnobs/issues) first. When filing a bug, include:
 
 - A clear, descriptive title
 - Steps to reproduce, and expected vs. actual behaviour
@@ -92,6 +92,6 @@ Please **do not** open a public issue for security vulnerabilities. See [SECURIT
 
 ## Questions?
 
-If you're unsure whether something is a good fit, open an issue and ask, or start a [discussion](https://github.com/Coffey-Labs/cairnobs/discussions). Discussion before you invest time in a PR is welcome.
+If you're unsure whether something is a good fit, [open an issue](https://git.coffeylabs.org/coffey-labs/cairnobs/issues) and ask. Discussion before you invest time in a PR is welcome.
 
 Thanks again for helping improve Cairn OBS.