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- self-host-overpass README + roadmap: superseded for POIs by poi-index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>

packages/map-core/tsconfig.json

@@ -4,5 +4,11 @@
     "outDir": "dist",
     "rootDir": "src"
   },
-  "include": ["src"]
+  "include": ["src"],
+  // *.sync.test.ts use node:fs to compare committed generated files
+  // (osmium-filters.txt, poi-selectors.sql) against the selectors. They run
+  // under vitest (node builtins provided) but are excluded from `tsc` so
+  // map-core keeps its zero-dependency, node-free type surface. All other
+  // tests are still typechecked.
+  "exclude": ["node_modules", "build", "dist", "src/**/*.sync.test.ts"]
 }