feat(search): Nominatim as the last-resort geocoder (#573)

Supersedes #350 by @sendmebits, ported onto the current component layout with fixes from review.

Verified before merge: format, package boundaries, unit suite, build, and the browser tracking suite; a browser harness for the change where one applies; adversarial review applied.

Co-authored-by: sendmebits <[email protected]>

server/providers/regional.js

@@ -4,4 +4,8 @@ export {
 } from './regional/briefing.js';
 export { weatherEffectsProxy } from './regional/weather-effects.js';
 export { validRegionalPoint } from './regional/query.js';
-export { createRegionalPlaceProvider } from './regional/place.js';
+export {
+  createRegionalPlaceProvider,
+  createNominatimSearchProvider,
+  geocodeProxy,
+} from './regional/place.js';