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- self-host-overpass README + roadmap: superseded for POIs by poi-index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/roadmap.md

@@ -83,7 +83,7 @@ See `docs/ideas/` for pre-spec explorations:
 
 - `mobile-activity-recording/` — GPS tracking and activity logging from a native app
 - `mobile-nearby-sync/` — BLE-based proximity discovery
-- `self-host-overpass/` — Self-hosted Overpass API for POI overlays
+- `self-host-overpass/` — Self-hosted Overpass API (superseded for POI overlays by the shipped `poi-index`; revive only if we need Overpass QL or to own the surface-backfill upstream)
 - `instance-administration.md` — admin role, registration toggle, suspend/ban, federation blocklists, reports
 - `social-interactions.md` — local likes + comments (the foundation the federated kudos/comments attach to)
 - `activity-participants.md` — tag co-riders on shared activities, confirm/decline, federated mentions