Prime: dev-backup gets dailies + weeklies — DONE

[2026-10-02] Prime: dev-backup gets dailies + weeklies — DONE. Retention is now 48 hourly + newest of 30 days + newest of 12 ISO weeks (retention.py beside the script; second path guard on the NAS side; unit fails if kept ≠ expected). Live run 0739: deleted 1, 0 errors, 48 kept = expected. History before 09-30 was already gone; dailies accumulate from today.