Backend: Add data retention and deletion policy implementation for PII-adjacent fields

[greatest0fallt1me]

Description

Define and enforce retention rules for logs, audit records, and any PII-adjacent data (wallet addresses if treated as personal data). Provide deletion/anonymization tooling and documentation.

Requirements and context

• Must be secure and documented.
• Must align with company compliance requirements.

Suggested execution

git checkout -b chore/data-retention-policy

Implement changes

• Add scheduled cleanup job for old records (where allowed).
• Add redaction/anonymization utilities.
• Document policy and operational procedure.

Test and commit

npm test

Example commit message

docs(compliance): implement data retention tooling and policy docs

Guidelines

• Timeframe: 96 hours.