Use overpass.private.coffee as primary Overpass endpoint

Switch the Planner's primary Overpass endpoint from
overpass.kumi.systems to overpass.private.coffee. private.coffee is a
privacy-focused public Overpass instance that doesn't log queries,
which fits the Planner's privacy-first principle better than the
previous default. Keep overpass-api.de as the silent fallback for
resilience while the self-host-overpass change is in flight.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/planner/app/lib/overpass.ts

@@ -1,7 +1,7 @@
 import type { PoiCategory } from "@trails-cool/map-core";
 
 const OVERPASS_ENDPOINTS = [
-  "https://overpass.kumi.systems/api/interpreter",
+  "https://overpass.private.coffee/api/interpreter",
   "https://overpass-api.de/api/interpreter",
 ];