feat(block2): Ğ1 — publish a Ğ1 address + 'Pay in Ğ1' in chat (levels 1-2)

The optional Ğ1 (free currency) integration, per g1-integration.md.
- Profile: an optional 'Ğ1 address' field, persisted locally and published in
  your NIP-01 kind:0 metadata (separate from the Nostr key).
- commons_core: UserProfile/ProfileTransport carry a 'g1' field (round-trip
  tested).
- Chat: when the peer published a Ğ1 address, a 'Pay in Ğ1' app-bar action opens
  their wallet (url_launcher) so value moves in the wallet, not the app — copies
  the address as a fallback. No payment rails in-app (sharing-model §4.3).

NOTE (vjrj): the wallet deep-link uses the Cesium web wallet as a universal
fallback; swap the URI in chat_screen._payG1 for the Ğ1nkgo/Ğecko scheme you
prefer. Analyzer clean (both packages); profile transport test covers g1.

apps/app_seeds/lib/i18n/strings_en.g.dart

@@ -1167,6 +1167,12 @@ class Translations$profile$en {
 	/// en: 'A short line — what you grow, where'
 	String get aboutHint => 'A short line — what you grow, where';
 
+	/// en: 'Ğ1 address (optional)'
+	String get g1 => 'Ğ1 address (optional)';
+
+	/// en: 'So people can pay you in Ğ1 — separate from your key'
+	String get g1Hint => 'So people can pay you in Ğ1 — separate from your key';
+
 	/// en: 'Your identity'
 	String get yourId => 'Your identity';
 
@@ -1223,6 +1229,12 @@ class Translations$chat$en {
 
 	/// en: 'Set up sharing to send messages'
 	String get offline => 'Set up sharing to send messages';
+
+	/// en: 'Pay in Ğ1'
+	String get payG1 => 'Pay in Ğ1';
+
+	/// en: 'Ğ1 address copied — paste it in your wallet'
+	String get g1Copied => 'Ğ1 address copied — paste it in your wallet';
 }
 
 // Path: trust
@@ -2033,6 +2045,8 @@ extension on Translations {
 			'profile.nameHint' => 'How others see you',
 			'profile.about' => 'About',
 			'profile.aboutHint' => 'A short line — what you grow, where',
+			'profile.g1' => 'Ğ1 address (optional)',
+			'profile.g1Hint' => 'So people can pay you in Ğ1 — separate from your key',
 			'profile.yourId' => 'Your identity',
 			'profile.idHelp' => 'Share this so people can recognise you',
 			'profile.copy' => 'Copy',
@@ -2046,6 +2060,8 @@ extension on Translations {
 			'chat.send' => 'Send',
 			'chat.empty' => 'No messages yet — say hello',
 			'chat.offline' => 'Set up sharing to send messages',
+			'chat.payG1' => 'Pay in Ğ1',
+			'chat.g1Copied' => 'Ğ1 address copied — paste it in your wallet',
 			'trust.none' => 'No one vouches for them yet',
 			'trust.count' => ({required Object n}) => 'Vouched for by ${n}',
 			'trust.vouch' => 'I know this person',