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/test/data/plantare_test.dart

@@ -0,0 +1,86 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/db/database.dart';
+import 'package:tane/db/enums.dart';
+
+import '../support/test_support.dart';
+
+/// A Plantare is a reproduction commitment (data-model §2.7): create it, list
+/// it, mark it returned/forgiven, and remove it (soft-delete).
+void main() {
+  late AppDatabase db;
+  setUp(() => db = newTestDatabase());
+  tearDown(() => db.close());
+
+  test('records a commitment and lists it (globally and per variety)', () async {
+    final repo = newTestRepository(db);
+    final vid = await repo.addQuickVariety(label: 'Tomate rosa');
+    final id = await repo.createPlantare(
+      direction: PlantareDirection.iReturn,
+      varietyId: vid,
+      counterparty: 'Ana',
+      owedDescription: 'un puñado la próxima temporada',
+    );
+
+    final all = await repo.watchPlantares().first;
+    expect(all, hasLength(1));
+    expect(all.single.id, id);
+    expect(all.single.direction, PlantareDirection.iReturn);
+    expect(all.single.counterparty, 'Ana');
+    expect(all.single.status, PlantareStatus.open);
+    expect(all.single.madeOn, greaterThan(0));
+
+    final forVariety = await repo.watchPlantaresForVariety(vid).first;
+    expect(forVariety.single.id, id);
+    // A different variety has none.
+    final other = await repo.addQuickVariety(label: 'Judía');
+    expect(await repo.watchPlantaresForVariety(other).first, isEmpty);
+  });
+
+  test('marking it returned stamps the settle time; forgiving keeps it settled',
+      () async {
+    final repo = newTestRepository(db);
+    final id = await repo.createPlantare(direction: PlantareDirection.owedToMe);
+
+    await repo.setPlantareStatus(id, PlantareStatus.returned);
+    var row = (await repo.watchPlantares().first).single;
+    expect(row.status, PlantareStatus.returned);
+    expect(row.settledOn, isNotNull);
+
+    // Reopening clears the settle stamp.
+    await repo.setPlantareStatus(id, PlantareStatus.open);
+    row = (await repo.watchPlantares().first).single;
+    expect(row.status, PlantareStatus.open);
+    expect(row.settledOn, isNull);
+  });
+
+  test('deleting a commitment tombstones it (drops from the list)', () async {
+    final repo = newTestRepository(db);
+    final id = await repo.createPlantare(direction: PlantareDirection.iReturn);
+    expect(await repo.watchPlantares().first, hasLength(1));
+    await repo.deletePlantare(id);
+    expect(await repo.watchPlantares().first, isEmpty);
+  });
+
+  test('commitments survive a backup round-trip (in exportInventory/import)',
+      () async {
+    final repoA = newTestRepository(db);
+    final vid = await repoA.addQuickVariety(label: 'Maíz');
+    await repoA.createPlantare(
+      direction: PlantareDirection.iReturn,
+      varietyId: vid,
+      counterparty: 'Colectivo semillero',
+      owedDescription: 'una mazorca',
+    );
+
+    final snapshot = await repoA.exportInventory();
+    expect(snapshot.plantares, hasLength(1));
+
+    final dbB = newTestDatabase();
+    addTearDown(dbB.close);
+    final repoB = newTestRepository(dbB);
+    await repoB.importInventory(snapshot);
+    final onB = await repoB.watchPlantares().first;
+    expect(onB.single.counterparty, 'Colectivo semillero');
+    expect(onB.single.owedDescription, 'una mazorca');
+  });
+}