9 archive tables have zero retention/prune — unbounded growth, fleet-wide pattern (also on venus)

All 9 mars archive tables (comisionesArchive, periodosArchive, practicasArchive, practicaImagesArchive, practicaTeethArchive, practicaToothConductosArchive, studentAssignmentsArchive, teacherComisionMembershipsArchive, usersArchive) are written and NEVER pruned — zero retention job anywhere in the fleet's mars deployment (confirmed: all 14 pg_cron jobs touch only emailOutbox/notifications/appEvents/dbperfSnapshots). Found during the fleet pg_temp/grant sweep (2026-07-31) answering the legitimate-deleter enumeration for MARS-597. Design gap, not a MARS-597 blocker — flagged separately per pmmaster ruling since venus independently found the same shape (2 lanes, same pattern: legitimate deleter lives on the log sink, never the archive tables). Needs a retention/growth-bound decision (or an explicit accept-unbounded-growth call) — not urgent, no incident.