[INFRA] Add Automated Database Backups

[JoshuaAFerguson]

Implement automated database backup strategy.

Backup Schedule:

• Every 15 minutes (keep 24 hours)
• Daily backups (keep 30 days)
• Weekly backups (keep 1 year)

Implementation:

*/15 * * * * pg_dump streamspace | gzip > backup-$(date +%Y%m%d-%H%M).sql.gz

Acceptance Criteria:

• Automated backups running
• Backups stored in S3/GCS
• Restore tested monthly
• RTO/RPO documented

Files: scripts/backup.sh (NEW), cron/backups.yaml (NEW)