chore: repoint URLs at git.swaits.com and bump for release

Rewrites remaining github.com / git.sr.ht references to git.swaits.com,
translating GitHub URL shapes to Gitea's (/blob/<ref>/ -> /src/branch/<ref>/,
/tree/<tag> -> /src/tag/<tag>, /actions/workflows/X -> /actions?workflow=X,
/edit/ -> /_edit/).

Left pointing at GitHub on purpose: pull-request links (PRs were not migrated)
and GitHub-only surfaces Gitea lacks (security advisories, discussions).

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "workdays"
-version = "0.1.3"
+version = "0.1.4"
 edition = "2021"
 authors = ["Stephen Waits <steve@waits.net>"]
 description = "A Rust library for computing work days and handling work calendars, inspired by the WORKDAY function in Excel."