A NIP-09 kind-5 delete is only honoured by relays and was never applied
locally, so on refresh the persisted React Query cache and the Dexie spot
cache re-rendered a just-deleted spot for a few seconds until fresh data
(or the admin hidden-label query) filtered it out.
Add src/lib/localDeletions.ts: a device-local tombstone keyed by coord
and event id, written optimistically by useDeleteEntity on the owner path
(rolled back if signing/publishing fails). The shared filterAdminHidden/
filterAdminHiddenMixed now also drop tombstoned items, so every list hook
filters them from first render with no per-hook changes. useSkateSpot
returns null for a tombstoned spot, and cacheSpots/cacheSpot refuse and
evict tombstoned rows. Prune by tombstone only (callers use limits 8-2000,
so pruning by 'not in fresh result' would wipe valid cached spots).
