fix(ci): use --locked when installing cross, bump to v0.28.1

[JoshuaBatty]

The home crate v0.5.12 (a transitive dependency of cross) now requires Rust 1.88, but CI uses 1.85.0. This broke the v0.28.0 release build.

Using --locked ensures cross uses its own Cargo.lock with pinned compatible versions (home v0.5.3).

Also bumps version to v0.28.1 for the new release.

[cursor]

PR Summary

Install cross with --locked in CI and bump fuelup to v0.28.1.

• CI:
  • Install cross with --locked in .github/workflows/ci.yml.
• Versioning:
  • Bump fuelup to 0.28.1 in Cargo.toml and Cargo.lock.

^{Written by Cursor Bugbot for commit 10dc893. This will update automatically on new commits. Configure here.}

[github-actions]

LCOV of commit 10dc893 during CI #2297

Summary coverage rate:
  lines......: 86.6% (2654 of 3064 lines)
  functions..: 61.8% (408 of 660 functions)
  branches...: 64.1% (278 of 434 branches)

Files changed coverage rate: n/a