feat(block2): offline outbox — share now, publish when connected

Sender-side offline delivery hardening.
- OfferOutbox: a keystore-backed (no plaintext) queue of lot ids to publish
  later. Stores ids, not offers, so on flush each offer is rebuilt from the
  lot's CURRENT state — an offline edit is respected, a deleted lot drops out.
- flushOutbox(): on reconnect, republishes queued lots and clears them (no-op
  offline; drops ids whose lot is gone).
- Market screen: sharing offline parks the lots ('we'll share these when you're
  connected'); opening the market online auto-flushes the queue first.
- Wired via DI + TaneApp(outbox); i18n en/es/pt.

Tests: 4 outbox + 3 flush + market UI, 20 green. Analyzer clean for new code.

apps/app_seeds/lib/i18n/es.i18n.json

@@ -353,6 +353,7 @@
     "sharedCount": "Compartidas {n} semillas",
     "nothingToShare": "Marca antes algunas semillas para regalar, cambiar o vender",
     "useLocation": "Usar mi ubicación aproximada",
-    "locationFailed": "No se pudo obtener tu ubicación"
+    "locationFailed": "No se pudo obtener tu ubicación",
+    "queued": "Guardado — las compartiremos cuando tengas conexión"
   }
 }