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/en.i18n.json

@@ -367,6 +367,8 @@
     "nameHint": "How others see you",
     "about": "About",
     "aboutHint": "A short line — what you grow, where",
+    "g1": "Ğ1 address (optional)",
+    "g1Hint": "So people can pay you in Ğ1 — separate from your key",
     "yourId": "Your identity",
     "idHelp": "Share this so people can recognise you",
     "copy": "Copy",
@@ -383,7 +385,9 @@
     "hint": "Write a message…",
     "send": "Send",
     "empty": "No messages yet — say hello",
-    "offline": "Set up sharing to send messages"
+    "offline": "Set up sharing to send messages",
+    "payG1": "Pay in Ğ1",
+    "g1Copied": "Ğ1 address copied — paste it in your wallet"
   },
   "trust": {
     "none": "No one vouches for them yet",