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.

README.md

@@ -1,6 +1,6 @@
 # DongLoRa Examples
 
-Example scripts demonstrating the [Python client library](https://github.com/donglora/client-py).
+Example scripts demonstrating the [Python client library](https://git.swaits.com/donglora/client-py).
 
 ## Running
 
@@ -15,4 +15,4 @@ just bridge --mode server   # LoRa bridge over TCP
 
 ## Depends On
 
-- [`donglora`](https://github.com/donglora/client-py) — the Python client library
+- [`donglora`](https://git.swaits.com/donglora/client-py) — the Python client library