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

@@ -2,7 +2,7 @@
 
 USB multiplexer daemon — lets multiple applications share one DongLoRa
 dongle simultaneously. Speaks the **DongLoRa Protocol v2** wire protocol
-(see [`PROTOCOL.md`](https://github.com/donglora/firmware/blob/main/PROTOCOL.md)).
+(see [`PROTOCOL.md`](https://git.swaits.com/donglora/protocol-rs/src/branch/main/PROTOCOL.md)).
 
 ## What It Does
 
@@ -33,7 +33,7 @@ just run --tcp 5741 --port /dev/ttyACM0   # with options
 
 ## Depends On
 
-- [`donglora`](https://github.com/donglora/client-py) (>= 1.0) — the
+- [`donglora`](https://git.swaits.com/donglora/client-py) (>= 1.0) — the
   Python client library. Provides the wire-level frame codec, event
   parsers, and USB discovery helpers this mux is built on.