Journals: per-journal retention (0 = indefinite), storage sizes, download, download-before-delete, archive on retire/harvest

Landed 2026-09-07 (feat/dashboard-v2, uncommitted; Pass S3). Settings > System > Journals & storage: database + disk size, one row per journal (plant, tent, room, facility, grow log, learning, soft-cal) with retention in days (0 = forever), rows/oldest/estimated size, JSON + CSV download; a retention cut previews the count and offers ‘Download first (zip)’ before ‘Delete without download’; archived plants are immune. Grow records card: retiring a roster slot archives the plant journal + its tent’s entries for the run (plant_journal_archive), downloadable as a zip bundle / JSON / CSV. Hourly prune from the ingest loop. Verified on a local non-demo brain (preview 2 of 4 seeded rows, confirm, exports 200). Needs: Pi hotpatch, a real retire on the live roster, and the archive-on-harvest hook once the harvest flow exists (S6).