JS preload(): replaced N individual GET /api/geocode (concurrency 2) with
a single POST /api/geocode/batch — one HTTP roundtrip instead of up to
N/2 sequential ones. schedLoc debounce reduced 600→200ms.
Server geocode_batch(): ThreadPoolExecutor(max_workers=4) parallelises
Nominatim/reverse_geocoder calls instead of sequential loop. Deduplicates
coords before submitting futures. lru_cache absorbs duplicates within batch.
Pi geocode_batch_route(): deduplicate coords, removed stale 'if label:'
guard (label always non-empty after BUG-13 fix).
Mathieu Moran
e60b7d7d36