feat(server): include reason in null reverse geocoding logs (#20347)

* Clarify in log why reverse geocoding may return nothing

* Decrease log level for empty reverse geocoding response from warn to log

* Use a named constant for 25km

* Mention fallback to countries in the message

* Improve natural earth log message

* Decrease log level for empty reverse geocoding response from natural earth countries

server/src/constants.ts

@@ -55,6 +55,7 @@ export const MACHINE_LEARNING_AVAILABILITY_BACKOFF_TIME = Number(
 );
 
 export const citiesFile = 'cities500.txt';
+export const reverseGeocodeMaxDistance = 25_000;
 
 export const MOBILE_REDIRECT = 'app.immich:///oauth-callback';
 export const LOGIN_URL = '/auth/login?autoLaunch=0';