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/en.i18n.json

@@ -373,7 +373,12 @@
     "nothingToShare": "Mark some seeds to give, swap or sell first",
     "useLocation": "Use my approximate location",
     "locationFailed": "Couldn't get your location — check that location is on and the permission is granted",
-    "queued": "Saved — we'll share these when you're connected"
+    "queued": "Saved — we'll share these when you're connected",
+    "shareFailed": "Couldn't reach the community servers — your seeds weren't shared. Try again in a moment.",
+    "rangeLabel": "How far to look",
+    "rangeNear": "Very close",
+    "rangeArea": "Around here",
+    "rangeRegion": "My region"
   },
   "profile": {
     "title": "Your profile",