Replace the planner's Overpass proxy with a self-hosted POI index:
- map-core POI categories become structured tag selectors (single source of
truth) + osmium filter / classification helpers
- planner.pois PostGIS table (centroid points, GiST + category indexes)
- /api/pois serving route (session + same-origin + rate limit, 100 cap)
- lib/pois.ts client (renamed from overpass.ts; GET, quantized bbox)
- metrics: poi_api_requests_total + DB-collected index rows/age gauges;
drop overpass_* metrics
- remove /api/overpass proxy + dead OVERPASS_URLS on the planner service
(Journal surface backfill still uses it via code default)
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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