Inspired by BitChat's location-channel concept, reframed for skaters and
kept fully SkateSpots-native (own kind + tag conventions, no interop).
- New ephemeral kind 24899 tagged with a geohash `g` (documented in NIP.md)
- useSpotChat / useSendSpotChat hooks (polled, community-relay aware)
- SpotChat component: live message list, composer, author profiles,
Block/Neighborhood/City precision toggle, and light IRC-style flavor
(/me action messages, /who participant count)
- Spot detail pages now show a per-spot block-level channel
- Map gains a "Local Chat" sheet anchored to the map center with the
precision selector
Co-authored-by: shakespeare.diy <assistant@shakespeare.diy>
