feat(plantare): schema v12 — bilateral signed columns + repo

Adds the deferred bilateral columns to Plantares (plantare-bilateral.md
§"Schema delta"), all nullable/defaulted so v1 local rows coexist
untouched:

- pledgeId (the shared id both parties key their row by), debtorKey /
  creditorKey, debtorSignature / creditorSignature, movementId (the
  shared hand-over Movement for the provenance DAG), remoteState
  (proposed/accepted/declined — the handshake, distinct from status),
  returnKind (similar/workHours/other, default similar) + workHours.

Repo: createPlantare grows optional bilateral params; plantareByPledgeId
looks a row up by the shared id; applyPlantareSignatures counter-stamps
an incoming accept; setPlantareRemoteState records a decline. The
JSON codec carries every new field so they ride backups.

Versioned migration is guarded/idempotent like the others; schema v12
dumped, test helper regenerated, migration test covers v1..v11 → v12.
db + data + services 295/295 green.

apps/app_seeds/lib/data/export_import/inventory_json_codec.dart

@@ -230,6 +230,16 @@ class InventoryJsonCodec {
             'status': p.status.name,
             'settledOn': p.settledOn,
             'note': p.note,
+            // Bilateral signed form (plantare-bilateral.md).
+            'pledgeId': p.pledgeId,
+            'debtorKey': p.debtorKey,
+            'creditorKey': p.creditorKey,
+            'debtorSignature': p.debtorSignature,
+            'creditorSignature': p.creditorSignature,
+            'movementId': p.movementId,
+            'remoteState': p.remoteState?.name,
+            'returnKind': p.returnKind.name,
+            'workHours': p.workHours,
           },
       ],
       'sales': [
@@ -484,6 +494,17 @@ class InventoryJsonCodec {
               _enumOr(PlantareStatus.values, m['status'], PlantareStatus.open),
           settledOn: m['settledOn'] as int?,
           note: m['note'] as String?,
+          pledgeId: m['pledgeId'] as String?,
+          debtorKey: m['debtorKey'] as String?,
+          creditorKey: m['creditorKey'] as String?,
+          debtorSignature: m['debtorSignature'] as String?,
+          creditorSignature: m['creditorSignature'] as String?,
+          movementId: m['movementId'] as String?,
+          remoteState:
+              _enumOrNull(PlantareRemoteState.values, m['remoteState']),
+          returnKind: _enumOr(PlantareReturnKind.values, m['returnKind'],
+              PlantareReturnKind.similar),
+          workHours: (m['workHours'] as num?)?.toDouble(),
         );
       }),
       sales: _rows(root, 'sales', (m) {