cargo-shuttle: v0.56.1 update

Fixes

• Fixed incorrect warning about lowercase ‘shuttle.toml’
• Installer: Now respects CARGO_HOME and CARGO_INSTALL_ROOT

What's Changed

• fix: mcp release flow by @jonaro00 in #2077
• fix(installer): respect $CARGO_HOME and $CARGO_INSTALL_ROOT by @jonaro00 in #2078
• fix(cargo-shuttle): warn when only lowercase shuttle.toml file exists by @jonaro00 in #2079
• chore: cargo-shuttle 0.56.1 by @jonaro00 in #2081

Full Changelog: v0.56.0...v0.56.1