feat(block2): market screen — discover seeds near you (offers UI)

Wires the 'coming soon' market card to a real discovery screen (mockups 04/05):
- MarketScreen: opens an OfferTransport lazily; local-first, so it degrades to a
  human 'set up sharing' prompt when no relay/area is set or the net is down.
- Discovers offers by the saved coarse area, lists them with human reciprocity
  labels (gift/swap/for sale), 'near you' (never exact location), price only for
  sales. Config sheet to set area + community servers (no bundled public relays).
- Threaded via TaneApp(social, socialSettings) — null keeps the card 'coming
  soon' (so Block 1 tests pass unchanged); main wires it live.
- i18n en/es/pt (market.*), reuses share.* for type labels.

3 market widget tests + home tests green; app_seeds analyzes clean.

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

@@ -327,5 +327,23 @@
     "cutting": { "singular": "esqueje", "plural": "esquejes" },
     "grams": { "singular": "gramo", "plural": "gramos" },
     "count": { "singular": "semilla", "plural": "semillas" }
+  },
+  "market": {
+    "title": "Semillas cerca de ti",
+    "subtitle": "Lo que otras personas comparten cerca",
+    "notSetUp": "Aún no has configurado el compartir",
+    "notSetUpBody": "Añade un servidor comunitario y tu zona para ver y compartir semillas cerca. Todo se mantiene aproximado — nunca tu dirección exacta.",
+    "setUp": "Configurar el compartir",
+    "searching": "Buscando por tu zona…",
+    "empty": "Aún no hay semillas compartidas cerca de ti",
+    "near": "Cerca de ti",
+    "configTitle": "Configuración de compartir",
+    "areaLabel": "Código de zona",
+    "areaHelp": "Se mantiene aproximado a propósito — tu zona a grandes rasgos, nunca un punto exacto.",
+    "serversLabel": "Servidores comunitarios",
+    "serversHelp": "Una dirección por línea — de redes de semillas o colectivos, no de una empresa.",
+    "save": "Guardar",
+    "saved": "Guardado",
+    "wanted": "Busco"
   }
 }