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/profile_store.dart

@@ -0,0 +1,20 @@
+import '../security/secret_store.dart';
+
+/// Your own display name and short "about", persisted locally (keystore-backed,
+/// no plaintext at rest). The network copy is a published NIP-01 kind:0 event;
+/// this local copy prefills the editor and works offline.
+class ProfileStore {
+  ProfileStore(this._store);
+
+  final SecretStore _store;
+  static const _nameKey = 'tane.social.profile.name';
+  static const _aboutKey = 'tane.social.profile.about';
+
+  Future<String> name() async => (await _store.read(_nameKey)) ?? '';
+  Future<String> about() async => (await _store.read(_aboutKey)) ?? '';
+
+  Future<void> save({required String name, required String about}) async {
+    await _store.write(_nameKey, name.trim());
+    await _store.write(_aboutKey, about.trim());
+  }
+}