feat(plantare): surface product link + dates; spec the bilateral record

The Plantaré screen stored madeOn/dueBy/varietyId but showed none of them,
so it felt half-built. Surface what's already there (no schema change):

- watchPlantareViews() joins each commitment with its variety label
- tile shows the made-on date, a "Return by {date}" line (amber + "overdue"
  when an open promise is past due, via new seedWarning colour), the variety
  name, and taps through to /variety/:id
- add sheet gains an optional return-by date picker (createPlantare already
  took dueBy)
- variety detail shows a read-only commitments section (hidden when empty,
  no add button — honours the single hand-over door)
- i18n en/es/pt/ast; tests for the join, dueBy round-trip, tile, and section

Also specs the deferred two-sided record in docs/design/plantare-bilateral.md
(Nostr pubkey counterparty, PlantareTransport propose->accept->counter-sign,
deferred key/signature/movement columns, provenance DAG, reputation anchor),
with a faithful transcription of the paper Plantaré v0.4 (BAH-Semillero 2009,
CC-BY-SA). Cross-linked from data-model §2.7 and sharing-model §6.

apps/app_seeds/test/ui/plantares_screen_test.dart

@@ -0,0 +1,114 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:go_router/go_router.dart';
+import 'package:tane/app.dart' show materialLocaleFor;
+import 'package:tane/db/database.dart';
+import 'package:tane/db/enums.dart';
+import 'package:tane/i18n/strings.g.dart';
+import 'package:tane/ui/plantares_screen.dart';
+
+import '../support/test_support.dart';
+
+/// The Plantares screen used to hide the data it stored: no date, no link to
+/// the seed. These pin the surfaced version — a named, dated, tappable
+/// commitment with an overdue nudge.
+void main() {
+  late AppDatabase db;
+  setUp(() => db = newTestDatabase());
+  tearDown(() => db.close());
+
+  testWidgets('a tile names the linked seed and flags an overdue return-by',
+      (tester) async {
+    final repo = newTestRepository(db);
+    final vid = await repo.addQuickVariety(label: 'Tomate rosa');
+    await repo.createPlantare(
+      direction: PlantareDirection.iReturn,
+      varietyId: vid,
+      counterparty: 'Ana',
+      dueBy: DateTime(2000, 1, 1).millisecondsSinceEpoch, // long past → overdue
+    );
+
+    await tester.pumpWidget(
+      wrapScreen(repository: repo, child: const PlantaresScreen()),
+    );
+    await tester.pump(); // let the Drift stream emit
+    await tester.pump(const Duration(milliseconds: 100));
+
+    expect(find.textContaining('Tomate rosa'), findsOneWidget);
+    expect(find.textContaining('Ana'), findsOneWidget);
+    expect(find.textContaining('Return by'), findsOneWidget);
+    expect(find.textContaining('overdue'), findsOneWidget);
+    await disposeTree(tester);
+  });
+
+  testWidgets('an open commitment with no due date shows no overdue flag',
+      (tester) async {
+    final repo = newTestRepository(db);
+    final vid = await repo.addQuickVariety(label: 'Maíz');
+    await repo.createPlantare(
+      direction: PlantareDirection.owedToMe,
+      varietyId: vid,
+    );
+
+    await tester.pumpWidget(
+      wrapScreen(repository: repo, child: const PlantaresScreen()),
+    );
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100));
+
+    expect(find.textContaining('overdue'), findsNothing);
+    expect(find.textContaining('Return by'), findsNothing);
+    await disposeTree(tester);
+  });
+
+  testWidgets('tapping a linked commitment opens its variety', (tester) async {
+    final repo = newTestRepository(db);
+    final vid = await repo.addQuickVariety(label: 'Judía');
+    await repo.createPlantare(
+      direction: PlantareDirection.iReturn,
+      varietyId: vid,
+    );
+
+    LocaleSettings.setLocaleSync(AppLocale.en);
+    final router = GoRouter(
+      routes: [
+        GoRoute(
+          path: '/',
+          builder: (_, _) => const PlantaresScreen(),
+        ),
+        GoRoute(
+          path: '/variety/:id',
+          builder: (_, state) =>
+              Scaffold(body: Text('variety ${state.pathParameters['id']}')),
+        ),
+      ],
+    );
+    await tester.pumpWidget(
+      TranslationProvider(
+        child: RepositoryProvider.value(
+          value: repo,
+          child: MaterialApp.router(
+            routerConfig: router,
+            locale: materialLocaleFor(AppLocale.en.flutterLocale),
+            supportedLocales: AppLocaleUtils.supportedLocales,
+            localizationsDelegates: const [
+              GlobalMaterialLocalizations.delegate,
+              GlobalWidgetsLocalizations.delegate,
+              GlobalCupertinoLocalizations.delegate,
+            ],
+          ),
+        ),
+      ),
+    );
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100));
+
+    await tester.tap(find.byType(ListTile).first);
+    await tester.pumpAndSettle();
+
+    expect(find.text('variety $vid'), findsOneWidget);
+    await disposeTree(tester);
+  });
+}

apps/app_seeds/test/ui/theme_contrast_test.dart

@@ -48,5 +48,10 @@ void main() {
       expectAa(Colors.white, seedGreen, 'white on primary green');
       expectAa(Colors.white, seedAppBar, 'white on app-bar green');
     });
+
+    test('overdue warning text on every background it sits on', () {
+      expectAa(seedWarning, Colors.white, 'seedWarning on white');
+      expectAa(seedWarning, seedCanvas, 'seedWarning on canvas');
+    });
   });
 }

apps/app_seeds/test/ui/variety_detail_screen_test.dart

@@ -610,4 +610,35 @@ void main() {
     expect(find.byIcon(Icons.star_border), findsNothing);
     await disposeTree(tester);
   });
+
+  testWidgets('shows a commitments section only when the variety has one', (
+    tester,
+  ) async {
+    final repo = newTestRepository(db);
+    final id = await repo.addQuickVariety(label: 'Maize');
+
+    await tester.pumpWidget(
+      wrapDetail(
+        repository: repo,
+        varietyId: id,
+        species: newTestSpeciesRepository(db),
+      ),
+    );
+    await tester.pumpAndSettle();
+    // No commitments yet → the section stays hidden (progressive disclosure).
+    expect(find.byKey(const Key('detail.plantares')), findsNothing);
+
+    await repo.createPlantare(
+      direction: PlantareDirection.iReturn,
+      varietyId: id,
+      counterparty: 'Ana',
+      owedDescription: 'un puñado',
+    );
+    await tester.pumpAndSettle();
+
+    expect(find.byKey(const Key('detail.plantares')), findsOneWidget);
+    expect(find.textContaining('un puñado'), findsOneWidget);
+    expect(find.textContaining('Ana'), findsOneWidget);
+    await disposeTree(tester);
+  });
 }