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/database.dart

@@ -22,6 +22,7 @@ part 'database.g.dart';
     Parties,
     Attachments,
     ExternalLinks,
+    Plantares,
   ],
 )
 class AppDatabase extends _$AppDatabase {
@@ -29,7 +30,7 @@ class AppDatabase extends _$AppDatabase {
 
   /// Current schema version; also stamped into interchange exports so an
   /// importer knows which app generation wrote the file (data-model §7).
-  static const int currentSchemaVersion = 8;
+  static const int currentSchemaVersion = 9;
 
   @override
   int get schemaVersion => currentSchemaVersion;
@@ -138,6 +139,13 @@ class AppDatabase extends _$AppDatabase {
           await m.createTable(conditionChecks);
         }
       }
+      // v9: Plantares — reproduction commitments (data-model §2.7). Guarded so a
+      // half-migrated dev database re-runs cleanly (see the v7 note above).
+      if (from < 9) {
+        if (!await _hasTable('plantares')) {
+          await m.createTable(plantares);
+        }
+      }
     },
   );