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/app.dart

@@ -12,6 +12,7 @@ import 'services/coarse_location.dart';
 import 'services/message_store.dart';
 import 'services/offer_outbox.dart';
 import 'services/onboarding_store.dart';
+import 'services/profile_cache.dart';
 import 'services/profile_store.dart';
 import 'services/social_service.dart';
 import 'services/social_settings.dart';
@@ -44,6 +45,7 @@ class TaneApp extends StatelessWidget {
     this.outbox,
     this.messageStore,
     this.profileStore,
+    this.profileCache,
     this.showIntro = false,
     this.autoBackup,
     super.key,
@@ -57,6 +59,7 @@ class TaneApp extends StatelessWidget {
           outbox,
           messageStore,
           profileStore,
+          profileCache,
         );
 
   final VarietyRepository repository;
@@ -79,6 +82,9 @@ class TaneApp extends StatelessWidget {
 
   /// Optional local store for your own profile (name/about).
   final ProfileStore? profileStore;
+
+  /// Optional cache of peers' published display names.
+  final ProfileCache? profileCache;
   final bool showIntro;
 
   /// Drives silent periodic backups off the app lifecycle. Null in widget tests
@@ -96,6 +102,7 @@ class TaneApp extends StatelessWidget {
     OfferOutbox? outbox,
     MessageStore? messageStore,
     ProfileStore? profileStore,
+    ProfileCache? profileCache,
   ) {
     return GoRouter(
       initialLocation: showIntro ? '/intro' : '/',
@@ -118,7 +125,12 @@ class TaneApp extends StatelessWidget {
         if (social != null && socialSettings != null && messageStore != null)
           GoRoute(
             path: '/messages',
-            builder: (context, state) => ChatListScreen(store: messageStore),
+            builder: (context, state) => ChatListScreen(
+              store: messageStore,
+              social: social,
+              settings: socialSettings,
+              profileCache: profileCache,
+            ),
           ),
         if (social != null && socialSettings != null && profileStore != null)
           GoRoute(
@@ -137,6 +149,7 @@ class TaneApp extends StatelessWidget {
               settings: socialSettings,
               peerPubkey: state.pathParameters['pubkey']!,
               messageStore: messageStore,
+              profileCache: profileCache,
             ),
           ),
         GoRoute(