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/ui/market_screen.dart

@@ -5,6 +5,7 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 import '../data/variety_repository.dart';
 import '../i18n/strings.g.dart';
 import '../services/coarse_location.dart';
+import '../services/offer_outbox.dart';
 import '../services/social_service.dart';
 import '../services/social_settings.dart';
 import '../state/offers_cubit.dart';
@@ -18,6 +19,7 @@ class MarketScreen extends StatefulWidget {
     required this.social,
     required this.settings,
     this.location,
+    this.outbox,
     super.key,
   });
 
@@ -28,6 +30,10 @@ class MarketScreen extends StatefulWidget {
   /// null (tests, or a platform without it) the shortcut is hidden.
   final CoarseLocationProvider? location;
 
+  /// Optional offline outbox: parks shares attempted with no network and flushes
+  /// them on reconnect. Null in tests → sharing offline is simply a no-op.
+  final OfferOutbox? outbox;
+
   @override
   State<MarketScreen> createState() => _MarketScreenState();
 }
@@ -43,6 +49,10 @@ class _MarketScreenState extends State<MarketScreen> {
   }
 
   Future<void> _init() async {
+    // Only needed to flush the outbox; read here (while mounted) to avoid using
+    // context across the awaits below. Null when there's no outbox (e.g. tests).
+    final repo =
+        widget.outbox != null ? context.read<VarietyRepository>() : null;
     setState(() => _loading = true);
     final cubit = await createOffersCubit(widget.social, widget.settings);
     final area = await widget.settings.areaGeohash();
@@ -56,7 +66,20 @@ class _MarketScreenState extends State<MarketScreen> {
       _loading = false;
     });
     await previous?.close();
-    if (area.isNotEmpty && cubit.isOnline) await cubit.discover(area);
+    if (area.isNotEmpty && cubit.isOnline) {
+      // Flush anything parked while offline, then show what's out there.
+      final outbox = widget.outbox;
+      if (outbox != null && repo != null) {
+        await flushOutbox(
+          outbox: outbox,
+          cubit: cubit,
+          shareableLots: await repo.shareableLots(),
+          authorPubkeyHex: widget.social.publicKeyHex,
+          areaGeohash: area,
+        );
+      }
+      if (mounted) await cubit.discover(area);
+    }
   }
 
   Future<void> _openConfig() async {
@@ -73,7 +96,7 @@ class _MarketScreenState extends State<MarketScreen> {
   /// coarse area. Prompts for setup when the area isn't set.
   Future<void> _shareMine() async {
     final cubit = _cubit;
-    if (cubit == null || !cubit.isOnline) return;
+    if (cubit == null) return;
     final repo = context.read<VarietyRepository>();
     final messenger = ScaffoldMessenger.of(context);
     final t = context.t;
@@ -89,12 +112,23 @@ class _MarketScreenState extends State<MarketScreen> {
       messenger.showSnackBar(SnackBar(content: Text(t.market.nothingToShare)));
       return;
     }
+    final ids = lots.map((l) => l.lotId).toList();
+
+    // Offline: park it and tell the person we'll share it later.
+    if (!cubit.isOnline) {
+      await widget.outbox?.enqueue(ids);
+      if (!mounted) return;
+      messenger.showSnackBar(SnackBar(content: Text(t.market.queued)));
+      return;
+    }
+
     final count = await cubit.publishLots(
       lots,
       authorPubkeyHex: widget.social.publicKeyHex,
       areaGeohash: area,
     );
     if (!mounted) return;
+    await widget.outbox?.remove(ids); // published now, so unpark any duplicates
     messenger.showSnackBar(SnackBar(content: Text(t.market.sharedCount(n: count))));
     await cubit.discover(area); // refresh — now including the just-shared lots
   }
@@ -113,7 +147,7 @@ class _MarketScreenState extends State<MarketScreen> {
       appBar: AppBar(
         title: Text(t.market.title),
         actions: [
-          if (cubit != null && cubit.isOnline)
+          if (cubit != null && (cubit.isOnline || widget.outbox != null))
             IconButton(
               key: const Key('market.shareMine'),
               icon: const Icon(Icons.ios_share_outlined),