feat: add comprehensive audit trail for SBOM modifications

[vpetersson]

Implement structured tracking of all SBOM changes for attestation and compliance purposes. Every modification is now recorded with UTC timestamps and categorized by type.

Changes:

• Add AuditTrail and AuditEntry classes with categorized tracking (AUGMENTATION, ENRICHMENT, SANITIZATION, OVERRIDE)
• Write detailed audit_trail.txt file alongside SBOM output
• Display summary table in stdout showing modification counts
• Output full audit trail in GitHub Actions collapsible group
• Record augmentation: supplier, manufacturer, authors, licenses, VCS, lifecycle
• Record enrichment: per-component metadata from external sources
• Record sanitization: URL/PURL normalizations, rejections, stubs
• Record overrides: CLI/env component name, version, PURL changes
• Maintain backward compatibility via TransformationTracker alias
• Add 28 new tests for audit trail functionality
• Document feature in README with example outputs

[Copilot]

Pull request overview

This PR implements a comprehensive audit trail system for tracking all SBOM modifications during processing. The audit trail captures every change made to the SBOM, categorized by type (augmentation, enrichment, sanitization, override), with UTC timestamps for compliance and attestation purposes.

Changes:

• Added AuditEntry and AuditTrail classes to replace and extend the legacy TransformationTracker
• Integrated audit trail recording throughout SBOM processing pipeline (augmentation, enrichment, overrides)
• Output includes summary table, detailed audit_trail.txt file, and collapsible attestation group in GitHub Actions
• Maintained backward compatibility through TransformationTracker alias

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/test_console.py	Added 28 comprehensive tests for AuditEntry and AuditTrail functionality
sbomify_action/console.py	Implemented AuditEntry and AuditTrail classes with recording methods and output formatting
sbomify_action/enrichment.py	Integrated audit trail recording for component enrichment operations
sbomify_action/cli/main.py	Added audit trail initialization, finalization, and file output in main pipeline
sbomify_action/augmentation.py	Integrated audit trail recording for SBOM augmentation operations
README.md	Documented the audit trail feature with example outputs

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