v0.5.0

Minor release since v0.4.1:

- The default `cargo build` bakes `web/dist` into the binary; the opt-in
  `embed-web` feature became the opt-out `api-only` (docs/DECISIONS.md #88).
  The container image no longer pins AXGIT_STATIC_DIR and friends, so every
  setting can come from the config file or the environment.
- Optional TOML config file (/etc/axgit/axgit.toml), layered under the CLI
  flags and AXGIT_* variables (#87).
- The shell route table is single-sourced between the astro dev middleware
  and the server via dist/shell-routes.json; a page without a table entry
  now fails the build (#88).
- Packaging, API and architecture docs folded into README.md, api/README.md
  and web/README.md; docs/ is now just DECISIONS.md and ROADMAP.md (#89, #90).
- CI moved from Jenkins to GitHub Actions. This is the first tag to publish
  release tarballs (x86_64 + aarch64 musl, with SHA256SUMS) and a
  multi-platform GHCR image at ghcr.io/ptcookie/axgit (#91, #92).