chore: repoint remaining links at git.swaits.com

Rewrites lingering github.com / *.sr.ht references to this Gitea instance,
translating GitHub and Sourcehut URL shapes to Gitea's (/blob/<ref>/ and
sr.ht /tree/<ref>/item/ -> /src/branch/<ref>/, /tree/<tag> -> /src/tag/<tag>,
/actions/workflows/X -> /actions?workflow=X, /edit/ -> /_edit/).

Left pointing at the old hosts on purpose: pull-request links (PRs were not
migrated), forks that were never migrated, and GitHub-only surfaces Gitea
lacks. OpenPGP identity proofs are untouched by design.

pyproject.toml

@@ -26,8 +26,8 @@ dependencies = [
 donglora-mux = "donglora_mux:main"
 
 [project.urls]
-Repository = "https://github.com/donglora/mux-py"
-Homepage = "https://github.com/donglora/mux-py"
+Repository = "https://git.swaits.com/donglora/mux-py"
+Homepage = "https://git.swaits.com/donglora/mux-py"
 
 [dependency-groups]
 dev = ["ruff", "pytest", "pytest-cov", "pytest-asyncio"]