refactor(social): one shared relay connection per identity

Every feature (offers, messaging, trust, profile, the inbox listener) used
to open its OWN RelayPool via social.openSession — several sockets to the
same relays, more battery, and reconnection logic living only in the inbox
listener.

Add SocialConnection: ONE shared session per identity, lazily connected and
reused by all. It watches connectivity — dropping the session when the
network goes and reconnecting when it returns, announcing each change on a
sessions stream so the inbox listener re-subscribes automatically. Callers
get the session via connection.session() and never close it (the connection
owns its lifecycle); recreated/disposed on an identity switch.

- InboxService now consumes the shared connection (subscribes on its
  sessions stream) instead of owning its own socket + connectivity code.
- createOffersCubit + the chat/market/profile screens use the shared
  connection; dead createMessagesCubit/createTrustCubit factories removed.
- DI registers SocialConnection per identity; Bootstrap starts it (after
  the inbox subscribes); switchSocialAccount disposes + recreates it.

Tests: SocialConnection lifecycle (reuse, concurrent connect, offline drop +
reconnect, unreachable retry) with a fake opener + online stream; inbox test
updated. nostr added as a dev_dependency for the channel fake.

apps/app_seeds/lib/ui/chat_list_screen.dart

@@ -7,8 +7,7 @@ import '../i18n/strings.g.dart';
 import '../services/inbox_service.dart';
 import '../services/message_store.dart';
 import '../services/profile_cache.dart';
-import '../services/social_service.dart';
-import '../services/social_settings.dart';
+import '../services/social_connection.dart';
 import 'theme.dart';
 import 'unread_badge.dart';
 
@@ -17,16 +16,16 @@ import 'unread_badge.dart';
 class ChatListScreen extends StatefulWidget {
   const ChatListScreen({
     required this.store,
-    this.social,
-    this.settings,
+    this.connection,
     this.profileCache,
     this.inbox,
     super.key,
   });
 
   final MessageStore store;
-  final SocialService? social;
-  final SocialSettings? settings;
+
+  /// The shared relay connection, for resolving peers' published names.
+  final SocialConnection? connection;
   final ProfileCache? profileCache;
 
   /// App-wide inbox listener; the list reloads whenever it reports a change.
@@ -69,20 +68,18 @@ class _ChatListScreenState extends State<ChatListScreen> {
     unawaited(_resolveMissingNames(items));
   }
 
-  /// Fetches published names for peers we don't have cached yet, over one
-  /// session. Best effort; the list already shows short keys meanwhile.
+  /// Fetches published names for peers we don't have cached yet, over the shared
+  /// connection. Best effort; the list already shows short keys meanwhile.
   Future<void> _resolveMissingNames(List<ChatSummary> items) async {
-    final social = widget.social;
-    final settings = widget.settings;
+    final connection = widget.connection;
     final cache = widget.profileCache;
-    if (social == null || settings == null || cache == null) return;
+    if (connection == null || cache == null) return;
     final missing =
         items.map((c) => c.peerPubkey).where((p) => !_names.containsKey(p));
     if (missing.isEmpty) return;
-    final relays = await settings.relayUrls();
-    if (relays.isEmpty) return;
+    final session = await connection.session();
+    if (session == null) return;
     try {
-      final session = await social.openSession(relays);
       for (final peer in missing) {
         final profile = await session.profile.fetch(peer);
         if (profile != null && profile.name.isNotEmpty) {
@@ -90,7 +87,6 @@ class _ChatListScreenState extends State<ChatListScreen> {
           if (mounted) setState(() => _names[peer] = profile.name);
         }
       }
-      await session.close();
     } catch (_) {
       // offline / unreachable — short keys stay.
     }

apps/app_seeds/lib/ui/chat_screen.dart

@@ -10,8 +10,8 @@ import '../di/injector.dart';
 import '../i18n/strings.g.dart';
 import '../services/message_store.dart';
 import '../services/profile_cache.dart';
+import '../services/social_connection.dart';
 import '../services/social_service.dart';
-import '../services/social_settings.dart';
 import '../services/trust_referents.dart';
 import '../services/unread_service.dart';
 import '../services/wot_settings.dart';
@@ -25,7 +25,7 @@ import 'theme.dart';
 class ChatScreen extends StatefulWidget {
   const ChatScreen({
     required this.social,
-    required this.settings,
+    required this.connection,
     required this.peerPubkey,
     this.messageStore,
     this.profileCache,
@@ -35,7 +35,9 @@ class ChatScreen extends StatefulWidget {
   });
 
   final SocialService social;
-  final SocialSettings settings;
+
+  /// The shared relay connection (one per identity), carrying messaging + trust.
+  final SocialConnection connection;
   final String peerPubkey;
 
   /// Optional persistence for chat history (keystore-backed); null in tests.
@@ -53,7 +55,6 @@ class ChatScreen extends StatefulWidget {
 }
 
 class _ChatScreenState extends State<ChatScreen> {
-  SocialSession? _session;
   MessagesCubit? _messages;
   TrustCubit? _trust;
   bool _loading = true;
@@ -79,25 +80,14 @@ class _ChatScreenState extends State<ChatScreen> {
   }
 
   Future<void> _init() async {
-    // One session for this chat carries both messaging and trust (the shared-
-    // connection shape). Offline (no relays / unreachable) → null transports.
-    final relays = await widget.settings.relayUrls();
-    SocialSession? session;
-    if (relays.isNotEmpty) {
-      try {
-        session = await widget.social.openSession(relays);
-      } catch (_) {
-        session = null;
-      }
-    }
+    // The shared connection carries both messaging and trust. Offline (not
+    // connected / unreachable) → null transports and the screen degrades.
+    final session = await widget.connection.session();
     final cachedName = await widget.profileCache?.name(widget.peerPubkey);
     final referents = await widget.trustReferents?.all() ?? const <String>{};
     final wotParams =
         await widget.wotSettings?.params() ?? WotParams.duniter;
-    if (!mounted) {
-      await session?.close();
-      return;
-    }
+    if (!mounted) return; // shared session is owned by the connection, not us
     final self = widget.social.publicKeyHex;
     final messages = MessagesCubit(
       session?.messages,
@@ -114,7 +104,6 @@ class _ChatScreenState extends State<ChatScreen> {
     );
     unawaited(trust.load());
     setState(() {
-      _session = session;
       _messages = messages;
       _trust = trust;
       _peerName = cachedName;
@@ -184,7 +173,7 @@ class _ChatScreenState extends State<ChatScreen> {
     unawaited(_unread?.markRead(widget.peerPubkey));
     _messages?.close();
     _trust?.close();
-    _session?.close();
+    // The session belongs to the shared connection — don't close it here.
     _input.dispose();
     super.dispose();
   }

apps/app_seeds/lib/ui/market_offer_detail_screen.dart

@@ -7,8 +7,7 @@ import 'package:go_router/go_router.dart';
 
 import '../i18n/strings.g.dart';
 import '../services/profile_cache.dart';
-import '../services/social_service.dart';
-import '../services/social_settings.dart';
+import '../services/social_connection.dart';
 import 'market_widgets.dart';
 import 'theme.dart';
 
@@ -20,16 +19,16 @@ import 'theme.dart';
 class MarketOfferDetailScreen extends StatefulWidget {
   const MarketOfferDetailScreen({
     required this.offer,
-    required this.social,
-    required this.settings,
+    required this.connection,
     this.mine = false,
     this.profileCache,
     super.key,
   });
 
   final Offer offer;
-  final SocialService social;
-  final SocialSettings settings;
+
+  /// The shared relay connection, for fetching the author's published profile.
+  final SocialConnection connection;
 
   /// Whether this is the current user's own listing (hide the message button).
   final bool mine;
@@ -43,7 +42,6 @@ class MarketOfferDetailScreen extends StatefulWidget {
 }
 
 class _MarketOfferDetailScreenState extends State<MarketOfferDetailScreen> {
-  SocialSession? _session;
   String? _sellerName;
   String? _sellerAbout;
   String? _sellerG1;
@@ -61,20 +59,8 @@ class _MarketOfferDetailScreenState extends State<MarketOfferDetailScreen> {
     final cachedName = await widget.profileCache?.name(widget.offer.authorPubkeyHex);
     if (mounted && cachedName != null) setState(() => _sellerName = cachedName);
 
-    final relays = await widget.settings.relayUrls();
-    SocialSession? session;
-    if (relays.isNotEmpty) {
-      try {
-        session = await widget.social.openSession(relays);
-      } catch (_) {
-        session = null;
-      }
-    }
-    if (!mounted) {
-      await session?.close();
-      return;
-    }
-    _session = session;
+    final session = await widget.connection.session();
+    if (!mounted) return;
     if (session == null) {
       setState(() => _profileLoading = false);
       return;
@@ -100,11 +86,7 @@ class _MarketOfferDetailScreenState extends State<MarketOfferDetailScreen> {
     }
   }
 
-  @override
-  void dispose() {
-    _session?.close();
-    super.dispose();
-  }
+  // No dispose of the session — it belongs to the shared connection.
 
   Future<void> _copyId() async {
     final t = context.t;

apps/app_seeds/lib/ui/market_screen.dart

@@ -8,6 +8,7 @@ import '../i18n/strings.g.dart';
 import '../services/coarse_location.dart';
 import '../services/discovery_area.dart';
 import '../services/offer_outbox.dart';
+import '../services/social_connection.dart';
 import '../services/social_service.dart';
 import '../services/social_settings.dart';
 import '../state/offers_cubit.dart';
@@ -21,6 +22,7 @@ class MarketScreen extends StatefulWidget {
   const MarketScreen({
     required this.social,
     required this.settings,
+    required this.connection,
     this.location,
     this.outbox,
     super.key,
@@ -29,6 +31,9 @@ class MarketScreen extends StatefulWidget {
   final SocialService social;
   final SocialSettings settings;
 
+  /// The shared relay connection (one per identity), reused for discovery.
+  final SocialConnection connection;
+
   /// Optional device-location source for the "use my location" shortcut; when
   /// null (tests, or a platform without it) the shortcut is hidden.
   final CoarseLocationProvider? location;
@@ -58,11 +63,8 @@ class _MarketScreenState extends State<MarketScreen> {
     final repo =
         widget.outbox != null ? context.read<VarietyRepository>() : null;
     setState(() => _loading = true);
-    final cubit = await createOffersCubit(
-      widget.social,
-      widget.settings,
-      repository: repo,
-    );
+    final cubit =
+        await createOffersCubit(widget.connection, repository: repo);
     final area = await widget.settings.areaGeohash();
     if (!mounted) {
       await cubit.close();

apps/app_seeds/lib/ui/profile_screen.dart

@@ -7,8 +7,8 @@ import '../i18n/strings.g.dart';
 import '../services/profile_cache.dart' show shortPubkey;
 import '../services/social_account_store.dart';
 import '../services/profile_store.dart';
+import '../services/social_connection.dart';
 import '../services/social_service.dart';
-import '../services/social_settings.dart';
 import 'qr_view.dart';
 import 'restart_widget.dart';
 import 'theme.dart';
@@ -19,7 +19,7 @@ import 'theme.dart';
 class ProfileScreen extends StatefulWidget {
   const ProfileScreen({
     required this.social,
-    required this.settings,
+    required this.connection,
     required this.profileStore,
     required this.accounts,
     this.trustNetworkEnabled = false,
@@ -27,7 +27,9 @@ class ProfileScreen extends StatefulWidget {
   });
 
   final SocialService social;
-  final SocialSettings settings;
+
+  /// The shared relay connection, for publishing your profile.
+  final SocialConnection connection;
   final ProfileStore profileStore;
   final SocialAccountStore accounts;
 
@@ -121,20 +123,16 @@ class _ProfileScreenState extends State<ProfileScreen> {
     await widget.profileStore
         .save(name: _name.text, about: _about.text, g1: _g1.text);
 
-    // Best-effort publish to the network so peers see the name.
-    final relays = await widget.settings.relayUrls();
-    if (relays.isNotEmpty) {
-      try {
-        final session = await widget.social.openSession(relays);
-        await session.profile.publish(
-          name: _name.text.trim(),
-          about: _about.text.trim(),
-          g1: _g1.text.trim(),
-        );
-        await session.close();
-      } catch (_) {
-        // offline / unreachable — the local copy is saved regardless.
-      }
+    // Best-effort publish over the shared connection so peers see the name.
+    try {
+      final session = await widget.connection.session();
+      await session?.profile.publish(
+        name: _name.text.trim(),
+        about: _about.text.trim(),
+        g1: _g1.text.trim(),
+      );
+    } catch (_) {
+      // offline / unreachable — the local copy is saved regardless.
     }
     if (!mounted) return;
     setState(() => _saving = false);