Relay outages no longer look like 'no spots'. querySkateContent swallowed every
relay error and returned [], so a dead relay would blank the map AND overwrite
good cached data with an empty list (then persist it). Now:
- querySkateContent/queryCanonical take an opt-in 'requireAny' that throws when
NO relay answered. Only the map's own feeds use it, so the blast radius is
small (79 other call sites keep today's behaviour).
- useSkateSpots/useSkateSpot fall back to the local IndexedDB cache on failure,
so the map still works at the park; they only error when nothing is saved.
- The persister refuses to persist an empty array, so an outage can't wipe the
last-known map on the next cold start.
- MapPage shows an honest 'Offline · showing saved spots' banner (reusing the
existing relayProbe/useRelayStatus) and a 'Can't reach the relays' card
instead of falsely claiming 'No spots mapped yet'.
Also seeds skater@skate-spots.org for the second admin (caba497f…) and reserves
the name so nobody else can claim it.