Enforce supply chain security for repository

[emmanuelknafo]

Summary

Comprehensive supply chain security audit and enforcement for the repository.

Changes

• Remove exposed Azure Storage key from appsettings.json files
• Update vulnerable NuGet packages (Microsoft.Data.SqlClient, System.Text.Json, Newtonsoft.Json)
• Enhance CODEOWNERS with security-sensitive path protection
• Update SECURITY.md with project-specific vulnerability reporting process
• Add SBOM attestation to build workflow (SLSA Level 2+)
• Add container signing preparation to CI workflow

Security Findings Addressed

• CRITICAL: Removed exposed Azure Storage key
• HIGH: Updated 3 vulnerable dependencies (CVE-2024-0056, CVE-2024-0057, CVE-2024-21907)
• HIGH: Enhanced governance controls
• HIGH: Added build provenance attestation

Follow-up Required

• Rotate Azure Storage key in Azure Portal
• Configure branch protection rules
• Verify attestations in next build