feat(counties): right-click to re-derive a US county from the ULS database

The automatic pass fills a blank county only, and deliberately: a value the
operator or QRZ supplied usually beats one derived from a ZIP code. That leaves
no way at all to correct a county already stored — and the Connecticut planning
regions are exactly that case. Every CT contact logged before that correction
holds a county the state abolished in 2022, and filling blanks never reaches
one of them.

So the new entry OVERWRITES, because it is asked for by hand on a chosen set of
rows precisely because the stored value is believed wrong. Only US entities are
touched, only callsigns the database holds, and only when the answer actually
differs — so re-running it on a mixed selection is safe and the count reported
is the number of counties that really changed. Award refs are re-materialised:
the county IS the reference for CQ USA-CA and the state for WAS.

The entry appears only once the database has been downloaded, and appears
without a restart when one finishes — an action that can only ever answer "no
database" is not worth a line in a menu this long.

frontend/src/components/NetControlPanel.tsx

@@ -49,6 +49,7 @@ type QSOMenuHandlers = {
   onUpdateFromCty?: (ids: number[]) => void;
   onUpdateFromQRZ?: (ids: number[]) => void;
   onUpdateFromClublog?: (ids: number[]) => void;
+  onUpdateCountyFromULS?: (ids: number[]) => void;
   onSendTo?: (service: string, ids: number[]) => void;
   onSendRecording?: (ids: number[]) => void;
   onSendEQSL?: (ids: number[]) => void;