feat:Setup production deployment checklist and verification

[bibi-fay]

Summary

This PR introduces a structured framework for code cleanup, deprecation management, and deployment verification.

Code Cleanup

• Added dead code analysis tooling using ts-prune and depcheck
• Introduced deprecation decorator and logging utilities
• Added deprecation registry for tracking legacy components
• Added GitHub Action for automated cleanup audits
• Created deprecation policy and removal timeline documentation

Deployment Governance

• Added deployment checklist and operational runbook
• Implemented environment validation scripts
• Added database backup verification
• Added pre-deployment verification checks
• Added post-deployment health check automation
• Added deployment verification workflow

Acceptance Criteria Mapping

Dead Code Cleanup

✅ Dead code identified and removable via audit tooling

✅ Unused dependencies detectable

✅ Deprecated functionality registry introduced

✅ Deprecation notices added

✅ Removal timeline documented

✅ Documentation updated

Deployment Checklist

✅ Deployment checklist created

✅ Pre-deployment verification script

✅ Post-deployment health checks

✅ Database backup verification

✅ Configuration verification

✅ Rollback procedure documented

✅ Deployment runbook created

Testing

• Verified cleanup scripts execute successfully
• Verified environment validation fails for missing variables
• Verified health check script validates deployment endpoints
• Verified GitHub Actions workflows execute successfully

Risk

Low. Changes are additive and do not modify business logic.

Closes #539
Closes #531

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