feat(data-retention): add automated pruning for audit logs and analyt…

[Adeyemi-cmd]

Close #848

PR Description

Summary

GDPR Article 5(1)(e) requires data to not be kept longer than necessary.
Audit logs and analytics events were accumulating indefinitely with no
automated pruning, degrading query performance and creating compliance risk.

Changes

Environment Variables

• AUDIT_LOG_RETENTION_DAYS — audit log retention period (default 730 = 2 years)
• ANALYTICS_RETENTION_DAYS — analytics event retention period (default 365 = 1 year)
• Both added to .env.example, env.validation.ts (Joi), and retention.config.ts

AuditRetentionTask (src/audit-log/tasks/audit-retention.task.ts)

• Rewritten to read AUDIT_LOG_RETENTION_DAYS from config
• Deletes expired rows in batches of 1000 (do...while loop with .limit())
• Increments deleted_count{table="audit_logs"} Prometheus counter per run
• Retains daily 2 AM cron schedule and weekly report handler

AnalyticsRetentionTask (src/analytics/tasks/analytics-retention.task.ts) [NEW]

• Reads ANALYTICS_RETENTION_DAYS from config (default 365)
• Deletes AnalyticsEvent rows where timestamp < cutoff in batches of 1000
• Runs daily at 2:30 AM (staggered from audit retention to avoid DB contention)
• Increments deleted_count{table="analytics_events"} Prometheus counter

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[RUKAYAT-CODER]

Great work on this PR
I really appreciate the effort you put into this—everything
kindly fix your workflow