fix(money): build reference model with Concerto 4

[niallroche]

Summary

Fixes the standalone build of money-reference@1.0.0.cto.

The model uses a Concerto map, but previously declared Concerto ^3.0.0, where map support is not enabled by default. It also imported money@1.0.0 without a resolvable source URL.

Changes

• Declare Concerto ^4.0.0, where map support is enabled by default.
• Resolve the org.accordproject.money@1.0.0.Unit import from the published Accord Project model URL.

Flags

• This is a model-only fix; no change to build.js is required.
• The model namespace and model version remain org.accordproject.money.reference@1.0.0.
• Verified using the repository's existing build process with Concerto 4.0.2.

Screenshots or Video

Not applicable.

Related Issues

• Issue Discussion: distribution channel & helper functions for money@1.0.0 reference data #187
• Pull Request feat(money): propose org.accordproject.money@1.0.0 + reference registries #188

Author Checklist

• Ensure you provide a DCO sign-off for your commits using the --signoff option of git commit.
• Vital features and changes captured in unit and/or integration tests
• Commits messages follow AP format
• Extend the documentation, if necessary
• Merging to master from niallroche:codex/fix-money-reference-build