fix(market): search your zone by a coarse prefix, not the exact cell

Discovery searched the full 5-char geohash (~2.4 km) with an exact Nostr tag
match, so two devices in adjacent cells never found each other even though
publish emits the full NIP-52 prefix ladder. Search now coarsens the area to a
configurable precision (SocialSettings.searchPrecision, default 4 ~20 km) via
searchPrefix(), with a human-worded 'how far' selector (Very close / Around
here / My region -> 5/4/3) in the market setup sheet.

Also: surface a clear 'couldn't reach the servers' message when no relay
accepts a share (instead of 'shared 0'), and add wss://relay.comunes.org as the
first default relay (reliable community home; public relays are backup).

Tests: settings precision (default/clamp/roundtrip), searchPrefix helper,
neighbour-cell discovery regression (offers_cubit + commons_core nostr
transports), and the range-selector widget test.

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

@@ -372,7 +372,12 @@
     "nothingToShare": "Marca antes algunas semillas para regalar, cambiar o vender",
     "useLocation": "Usar mi ubicación aproximada",
     "locationFailed": "No se pudo obtener tu ubicación — comprueba que la ubicación está activada y el permiso concedido",
-    "queued": "Guardado — las compartiremos cuando tengas conexión"
+    "queued": "Guardado — las compartiremos cuando tengas conexión",
+    "shareFailed": "No se pudo conectar con los servidores — tus semillas no se compartieron. Inténtalo de nuevo en un momento.",
+    "rangeLabel": "Hasta dónde buscar",
+    "rangeNear": "Muy cerca",
+    "rangeArea": "Por mi zona",
+    "rangeRegion": "Mi región"
   },
   "profile": {
     "title": "Tu perfil",