feat(block2): publish my seeds to the network (completes publish->discover)

The other half of the market: share your marked lots as offers.
- VarietyRepository.shareableLots(): non-private lots WITH their id (stable,
  updatable offer id) + the variety label. Private lots never leave the device.
- OffersCubit.publishLots(): maps each via OfferMapper and publishes, tagged
  with the coarse area + signed by the derived key; counts acceptances; no-op
  offline or with no area.
- Market screen: a 'share my seeds' action (online only) — publishes, then
  re-discovers to show them; 'mark some seeds first' when nothing's shared.
- i18n en/es/pt.

14 tests green (repo query, cubit publish, market UI); analyzer clean for new code.

apps/app_seeds/lib/state/offers_cubit.dart

@@ -4,6 +4,8 @@ import 'package:commons_core/commons_core.dart';
 import 'package:equatable/equatable.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
+import '../data/variety_repository.dart';
+import '../services/offer_mapper.dart';
 import '../services/social_service.dart';
 import '../services/social_settings.dart';
 
@@ -119,6 +121,39 @@ class OffersCubit extends Cubit<OffersState> {
     }
   }
 
+  /// Publishes the user's [lots] as offers, each tagged with the coarse
+  /// [areaGeohash] and signed by [authorPubkeyHex]. Returns how many the relay
+  /// accepted. No-op (returns 0) when offline or with no area set.
+  Future<int> publishLots(
+    List<ShareableLot> lots, {
+    required String authorPubkeyHex,
+    required String areaGeohash,
+  }) async {
+    final transport = _transport;
+    if (transport == null || areaGeohash.isEmpty || lots.isEmpty) return 0;
+    emit(state.copyWith(publishing: true, error: () => null));
+    var accepted = 0;
+    try {
+      for (final lot in lots) {
+        final offer = OfferMapper.fromSharedLot(
+          lotId: lot.lotId,
+          authorPubkeyHex: authorPubkeyHex,
+          summary: lot.summary,
+          sharing: lot.offerStatus,
+          areaGeohash: areaGeohash,
+          category: lot.category,
+        );
+        final result = await transport.publish(offer);
+        if (result.accepted) accepted++;
+      }
+      emit(state.copyWith(publishing: false));
+    } catch (e) {
+      emit(state.copyWith(publishing: false, error: () => '$e'));
+      rethrow;
+    }
+    return accepted;
+  }
+
   @override
   Future<void> close() async {
     await _sub?.cancel();