Completes the Location feature (schema + migration landed earlier under 98cabc5).
- Hierarchical Location model is the shared spine; unlimited nesting
- Garden add/edit now picks a reusable Location (inline create) instead of
freeform text; garden groups By Location off the real tree
- Dual-write keeps legacy Plant.zone in sync with location.name (Release A)
- /api/locations CRUD + /api/locations/[id]/log (logs a location + its sub-locations)
- Location tree pure-core (buildTree/computePath/descendantIds) with tests
- Location added to backup/restore export
- Bump APP_VERSION 0.10.0 + plain-English changelog entry
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
