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/es.i18n.json

@@ -367,6 +367,8 @@
     "nameHint": "Cómo te ven los demás",
     "about": "Sobre ti",
     "aboutHint": "Una línea — qué cultivas, dónde",
+    "g1": "Dirección Ğ1 (opcional)",
+    "g1Hint": "Para que te paguen en Ğ1 — aparte de tu clave",
     "yourId": "Tu identidad",
     "idHelp": "Compártela para que te reconozcan",
     "copy": "Copiar",
@@ -383,7 +385,9 @@
     "hint": "Escribe un mensaje…",
     "send": "Enviar",
     "empty": "Aún no hay mensajes — saluda",
-    "offline": "Configura el compartir para enviar mensajes"
+    "offline": "Configura el compartir para enviar mensajes",
+    "payG1": "Pagar en Ğ1",
+    "g1Copied": "Dirección Ğ1 copiada — pégala en tu cartera"
   },
   "trust": {
     "none": "Nadie los avala aún",