feat(block2): offline outbox — share now, publish when connected

Sender-side offline delivery hardening.
- OfferOutbox: a keystore-backed (no plaintext) queue of lot ids to publish
  later. Stores ids, not offers, so on flush each offer is rebuilt from the
  lot's CURRENT state — an offline edit is respected, a deleted lot drops out.
- flushOutbox(): on reconnect, republishes queued lots and clears them (no-op
  offline; drops ids whose lot is gone).
- Market screen: sharing offline parks the lots ('we'll share these when you're
  connected'); opening the market online auto-flushes the queue first.
- Wired via DI + TaneApp(outbox); i18n en/es/pt.

Tests: 4 outbox + 3 flush + market UI, 20 green. Analyzer clean for new code.

apps/app_seeds/lib/state/offers_cubit.dart

@@ -6,6 +6,7 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../data/variety_repository.dart';
 import '../services/offer_mapper.dart';
+import '../services/offer_outbox.dart';
 import '../services/social_service.dart';
 import '../services/social_settings.dart';
 
@@ -178,3 +179,31 @@ Future<OffersCubit> createOffersCubit(
     return OffersCubit(null); // offline / no relay reachable
   }
 }
+
+/// Publishes any queued (offline-parked) lots now that we're online, then clears
+/// them from the [outbox]. Rebuilds each offer from the lot's CURRENT state, so
+/// since-deleted or now-private lots simply drop out. Returns how many published.
+Future<int> flushOutbox({
+  required OfferOutbox outbox,
+  required OffersCubit cubit,
+  required List<ShareableLot> shareableLots,
+  required String authorPubkeyHex,
+  required String areaGeohash,
+}) async {
+  if (!cubit.isOnline || areaGeohash.isEmpty) return 0;
+  final queued = await outbox.pending();
+  if (queued.isEmpty) return 0;
+  final toPublish =
+      shareableLots.where((l) => queued.contains(l.lotId)).toList();
+  var published = 0;
+  if (toPublish.isNotEmpty) {
+    published = await cubit.publishLots(
+      toPublish,
+      authorPubkeyHex: authorPubkeyHex,
+      areaGeohash: areaGeohash,
+    );
+  }
+  // Clear everything attempted (or gone) so we don't loop on it.
+  await outbox.remove(queued);
+  return published;
+}