poi-index: Grafana dashboard/alert, docs, privacy manifest

- planner dashboard: replace Overpass panels with POI index freshness +
  serving panels (age, rows/category, import status, API request rate/errors)
- alerts: replace overpass-upstream-unhealthy with poi-index-stale (>6 weeks)
- architecture.md: POI data flow now the self-hosted index
- privacy manifest (DE+EN): Overpass is Journal-surface-backfill-only;
  Planner POIs served same-origin from /api/pois
- self-host-overpass README + roadmap: superseded for POIs by poi-index
- poi-extract README: self-hoster story (optional pipeline, regional extract,
  graceful empty index)
- map-core tsconfig: exclude *.sync.test.ts from tsc to keep it zero-dep

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/architecture.md

@@ -790,8 +790,12 @@ Base layers:
 
 Overlays (toggleable):
 - **OpenCampingMap** (campsites, shelters — essential for bikepacking)
-- **POI overlay**: Water points, shelters, bike repair stations
-  (sourced from OSM Overpass API or pre-cached)
+- **POI overlay**: Water points, shelters, bike repair stations, etc. Served
+  from the instance's own `planner.pois` index via `/api/pois` — a PostGIS
+  table built monthly from an OSM extract (osmium filter on the BRouter host →
+  guarded atomic import on the flagship). No third-party POI service is
+  contacted; viewport coordinates never leave trails.cool. See the
+  `poi-index` change and `infrastructure/brouter-host/poi-extract/`.
 - **Waymarked Trails** (hiking/cycling trail networks)
 
 Implementation: Leaflet layer switcher with tile URLs. No API keys needed