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).

packages/commons_core/test/social/nostr_profile_test.dart

@@ -0,0 +1,46 @@
+import 'dart:typed_data';
+
+import 'package:commons_core/commons_core.dart';
+import 'package:test/test.dart';
+
+import '../support/mini_relay.dart';
+
+void main() {
+  Future<NostrIdentity> idFor(int fill) =>
+      NostrKeyDerivation.deriveFromSeed(Uint8List(32)..fillRange(0, 32, fill));
+
+  late MiniRelay relay;
+  setUp(() async => relay = await MiniRelay.start());
+  tearDown(() async => relay.stop());
+
+  test('publish then fetch round-trips a profile (kind:0)', () async {
+    final alice = await idFor(1);
+    final aliceConn = await NostrConnection.connect(relay.url, identity: alice);
+    await NostrProfileTransport(aliceConn)
+        .publish(name: 'Alicia', about: 'Guardo tomate rosa');
+
+    // Anyone else can fetch it.
+    final bob = await idFor(2);
+    final bobConn = await NostrConnection.connect(relay.url, identity: bob);
+    final fetched =
+        await NostrProfileTransport(bobConn).fetch(alice.publicKeyHex);
+
+    expect(fetched, isNotNull);
+    expect(fetched!.name, 'Alicia');
+    expect(fetched.about, 'Guardo tomate rosa');
+
+    await aliceConn.close();
+    await bobConn.close();
+  });
+
+  test('fetch returns null when the peer never published a profile', () async {
+    final me = await idFor(3);
+    final conn = await NostrConnection.connect(relay.url, identity: me);
+    final stranger = await idFor(9);
+    expect(
+      await NostrProfileTransport(conn).fetch(stranger.publicKeyHex),
+      isNull,
+    );
+    await conn.close();
+  });
+}