feat(block2): show contact names (resolve peers' published profiles)

Closes the profile loop — peers now appear by name, not a raw key.
- ProfileCache: keystore-backed cache of peers' published display names (works
  offline) + shortPubkey() fallback.
- Chat: the app bar shows the peer's name (cached first, then freshened from
  their kind:0 over the session); falls back to a short key.
- Inbox: each conversation shows the cached name, and missing names are resolved
  over one session and cached.
- Wired via DI + TaneApp(profileCache).

Analyzer clean; ProfileCache covered by a plain test.

apps/app_seeds/lib/ui/chat_screen.dart

@@ -5,6 +5,7 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../i18n/strings.g.dart';
 import '../services/message_store.dart';
+import '../services/profile_cache.dart';
 import '../services/social_service.dart';
 import '../services/social_settings.dart';
 import '../state/messages_cubit.dart';
@@ -20,6 +21,7 @@ class ChatScreen extends StatefulWidget {
     required this.settings,
     required this.peerPubkey,
     this.messageStore,
+    this.profileCache,
     super.key,
   });
 
@@ -30,6 +32,9 @@ class ChatScreen extends StatefulWidget {
   /// Optional persistence for chat history (keystore-backed); null in tests.
   final MessageStore? messageStore;
 
+  /// Optional cache of peer display names; null in tests.
+  final ProfileCache? profileCache;
+
   @override
   State<ChatScreen> createState() => _ChatScreenState();
 }
@@ -39,6 +44,7 @@ class _ChatScreenState extends State<ChatScreen> {
   MessagesCubit? _messages;
   TrustCubit? _trust;
   bool _loading = true;
+  String? _peerName;
   final _input = TextEditingController();
 
   @override
@@ -59,6 +65,7 @@ class _ChatScreenState extends State<ChatScreen> {
         session = null;
       }
     }
+    final cachedName = await widget.profileCache?.name(widget.peerPubkey);
     if (!mounted) {
       await session?.close();
       return;
@@ -77,8 +84,25 @@ class _ChatScreenState extends State<ChatScreen> {
       _session = session;
       _messages = messages;
       _trust = trust;
+      _peerName = cachedName;
       _loading = false;
     });
+
+    // Freshen the peer's name from their published profile.
+    final live = session;
+    if (live != null && widget.profileCache != null) {
+      unawaited(() async {
+        try {
+          final profile = await live.profile.fetch(widget.peerPubkey);
+          if (profile != null && profile.name.isNotEmpty && mounted) {
+            await widget.profileCache!.setName(widget.peerPubkey, profile.name);
+            setState(() => _peerName = profile.name);
+          }
+        } catch (_) {
+          // best effort
+        }
+      }());
+    }
   }
 
   Future<void> _send() async {
@@ -100,11 +124,12 @@ class _ChatScreenState extends State<ChatScreen> {
 
   @override
   Widget build(BuildContext context) {
-    final t = context.t;
     final messages = _messages;
     final trust = _trust;
     return Scaffold(
-      appBar: AppBar(title: Text(t.chat.title)),
+      appBar: AppBar(
+        title: Text(_peerName ?? shortPubkey(widget.peerPubkey)),
+      ),
       body: _loading || messages == null || trust == null
           ? const Center(child: CircularProgressIndicator())
           : MultiBlocProvider(