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.