Publish Contribution Guidelines, Extended Developer Docs, and CI/CD SBOM Integration

[DinneK]

• Publish a CONTRIBUTING.md and developer setup guide covering repo structure, PR process, and coding standards.
• Extend documentation to include architecture diagrams, deployment steps, and test workflows.
• Integrate automated SBOM (Software Bill of Materials) generation into CI/CD to meet SHARE IT Act and supply chain security requirements.

[decause-gov]

Useful link for SBOM integration: https://github.com/DSACMS/iv-cbv-payroll/dependency-graph/sbom