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.

CHANGELOG.md

@@ -552,7 +552,7 @@ supported board.
 ### Infrastructure
 
 - Cargo.toml `repository` + `homepage` now point at the canonical
-  `https://github.com/donglora/firmware` (the `swaits/donglora`
+  `https://git.swaits.com/donglora/firmware` (the `swaits/donglora`
   repo is archived).
 
 ## [0.5.0] - 2026-04-16