AuditLog and ProcessedWebhook grow unbounded — add TTL or archival

[projectamazonph]

Problem

Two tables grow without bound:

1. AuditLog — every admin mutation logs here (per ADR-014). No TTL, no partitioning, no archival strategy.
2. ProcessedWebhook — PayMongo webhook idempotency log. Old entries (>30 days) serve no purpose but accumulate forever.

Impact

• Slow queries on AuditLog as row count grows (admin dashboard, analytics)
• ProcessedWebhook becomes noise — idempotency window is hours, not months
• Storage costs on Neon increase monotonically

Suggested Fix

ProcessedWebhook: Add a scheduled cleanup job (e.g., Vercel cron or a script) that deletes rows older than 30 days.

AuditLog: Two options:

• Partition by month (Postgres native partitioning) — keeps queries fast, old partitions can be detached/archived
• Archive + truncate — export to cold storage, then delete rows older than 12 months

Either way, add a createdAt-based TTL policy.

References

• prisma/schema.prisma lines 816-833 (AuditLog)
• prisma/schema.prisma lines 762-779 (ProcessedWebhook)
• AGENTS.md rule 5: Every admin action logs to AuditLog

Severity: Consider — operational debt, not urgent but compounds over time