feat(plantare): UI — propose from chat, review & sign on the ledger

The viral loop, made usable end-to-end:

- Propose sheet (plantare_propose_sheet.dart): from a chat with a peer
  (their key already in hand), pick your side, name the seed, choose what
  comes back (similar · non-GMO organic / work hours / other) and an
  optional return-by, then sign and send. Reached from the chat overflow
  menu; confirms "waiting for them to sign".
- Plantares screen: incoming proposals show Accept & sign / Decline right
  on the tile; every bilateral row wears a handshake badge — awaiting
  signature, signed by both, or declined. Accept falls back to a gentle
  "offline" nudge if the proposal isn't in hand yet.
- i18n: full en + es for the bilateral flow; other locales fall back to
  base per slang config.

Wire-up only touches human copy (no jargon) and stays behind the
optional PlantareService, so inventory-only builds are unaffected.

Tests: propose sheet drives a real sign+send; the ledger renders the
signed/awaiting badges. Fake SocialSession in your_people test gains the
new transport getter. Widget tests targeted + timed. All green.

apps/app_seeds/test/ui/plantares_screen_test.dart

@@ -63,6 +63,57 @@ void main() {
     await disposeTree(tester);
   });
 
+  testWidgets('a fully-signed bilateral pledge shows the "signed by both" badge',
+      (tester) async {
+    LocaleSettings.setLocaleSync(AppLocale.en);
+    final repo = newTestRepository(db);
+    await repo.createPlantare(
+      direction: PlantareDirection.owedToMe,
+      counterparty: 'Ana',
+      pledgeId: 'p-1',
+      debtorKey: 'dk',
+      creditorKey: 'ck',
+      debtorSignature: 'ds',
+      creditorSignature: 'cs',
+      remoteState: PlantareRemoteState.accepted,
+    );
+
+    await tester.pumpWidget(
+      wrapScreen(repository: repo, child: const PlantaresScreen()),
+    );
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100));
+
+    expect(find.text('Signed by both'), findsOneWidget);
+    // No accept/decline for a closed deal.
+    expect(find.byKey(const Key('plantare.accept.')), findsNothing);
+    await disposeTree(tester);
+  });
+
+  testWidgets('a pending proposal shows the "awaiting signature" badge',
+      (tester) async {
+    LocaleSettings.setLocaleSync(AppLocale.en);
+    final repo = newTestRepository(db);
+    await repo.createPlantare(
+      direction: PlantareDirection.iReturn,
+      counterparty: 'Ben',
+      pledgeId: 'p-2',
+      debtorKey: 'dk',
+      creditorKey: 'ck',
+      creditorSignature: 'cs', // proposer (creditor) signed; I (debtor) haven't
+      remoteState: PlantareRemoteState.proposed,
+    );
+
+    await tester.pumpWidget(
+      wrapScreen(repository: repo, child: const PlantaresScreen()),
+    );
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100));
+
+    expect(find.text('Awaiting signature'), findsOneWidget);
+    await disposeTree(tester);
+  });
+
   testWidgets('tapping a linked commitment opens its variety', (tester) async {
     final repo = newTestRepository(db);
     final vid = await repo.addQuickVariety(label: 'Judía');