Make build-schema multi-project and improve template version handling

[albatalavera]

Summary

This PR extends build-schema to support project-specific schema/template generation and improves how metadata template version history is handled.

Changes

• Make build-schema project-aware.
• Use the selected project name to resolve default schemas and Excel templates.
• Add explicit --initial-version handling for first template releases.
• Preserve previous VERSION history when a template is provided or found in assets.
• Prevent incompatible use of --initial-version with --excel_template.
• Add Redlabra support for build-schema.

Notes

Redlabra can now generate its own outputs, such as:

• redlabra_schema.json
• redlabra_metadata_template_v*.xlsx

PR Checklist

• This comment contains a description of changes (with reason).
• Make sure your code lints (black and flake8).
• CHANGELOG.md is updated.
• README.md is updated (including new tool citations and authors/contributors).

[Aberdur]

LGTM 🚀