feat(plantare): reproduction-commitment data layer (schema v9)

The Plantare — a promise to reproduce seed and return some (data-model §2.7,
the seed-domain Pledge with return_kind=similar). NOT a sale. Local-first
v1: your honest ledger of commitments (from/to a person by name); the
bilateral signed cross-party form is a later social-layer phase.

- New Plantares table (SyncColumns): varietyId, direction (iReturn/owedToMe),
  counterparty, owedDescription, madeOn, dueBy, status (open/returned/
  forgiven), settledOn, note. schemaVersion 8 -> 9 with a guarded createTable
  migration; schema exported + migration-test helper regenerated.
- VarietyRepository: createPlantare / watchPlantares / watchPlantaresForVariety
  / setPlantareStatus / deletePlantare (soft-delete, CRDT-stamped).
- Included in backups + sync: InventorySnapshot + JSON codec (round-trips
  isDeleted) + exportInventory/exportForSync/importInventory, so commitments
  survive restore and replicate LWW like every other row.

Tests: v1..v8 -> v9 migration + fresh v9; repo create/list/settle/reopen/
delete; and a backup round-trip preserving a commitment. 13 green.

UI (detail section + Plantares screen) follows.

apps/app_seeds/lib/db/enums.dart

@@ -86,3 +86,18 @@ enum AttachmentKind { photo, doc }
 
 /// Polymorphic parent of an Attachment / ExternalLink.
 enum ParentType { variety, lot, movement }
+
+/// Whose reproduction promise a Plantare is, seen from this app's owner
+/// (data-model §2.7). A Plantare is a commitment to REPRODUCE and return seed —
+/// not a sale.
+enum PlantareDirection {
+  /// I received seed and promised to grow it out and return some.
+  iReturn,
+
+  /// I gave seed and the other person promised to return some.
+  owedToMe,
+}
+
+/// Lifecycle of a Plantare. Framed as a promise, not a debt (data-model §2.7):
+/// `forgiven` (not "defaulted") when it's let go.
+enum PlantareStatus { open, returned, forgiven }