feat(block2): profiles — your identity card + name/about (NIP-01 kind:0)

Drawer 'Profile' is now live.
- commons_core: ProfileTransport + UserProfile + NostrProfileTransport (kind:0
  publish/fetch), exposed as SocialSession.profile. Round-trip tested against the
  in-process relay (fast dart test).
- app: ProfileStore (local name/about, keystore) + ProfileScreen — shows your
  shareable npub with copy, edits display name + 'about', saves locally and (when
  online) publishes kind:0 so peers can recognise you instead of a raw key.
- Drawer 'Profile' -> /profile (gated like Market/Chat).
- i18n en/es/pt. ProfileStore + profile transport covered by plain/dart tests.

Analyzer clean (both packages).

apps/app_seeds/lib/services/social_service.dart

@@ -51,13 +51,15 @@ class SocialSession {
   SocialSession(this._channel)
       : offers = NostrOfferTransport(_channel),
         messages = NostrMessageTransport(_channel),
-        trust = NostrTrustTransport(_channel);
+        trust = NostrTrustTransport(_channel),
+        profile = NostrProfileTransport(_channel);
 
   final NostrChannel _channel;
 
   final OfferTransport offers;
   final MessageTransport messages;
   final TrustTransport trust;
+  final ProfileTransport profile;
 
   Future<void> close() => _channel.close();
 }