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.

app.go

@@ -10549,6 +10549,66 @@ func (a *App) applyULSCounty(q *qso.QSO) {
 	}
 }
 
+// UpdateQSOsCountyFromULS re-derives the county of the selected US contacts from
+// the offline ULS database, and OVERWRITES what is there.
+//
+// That is the difference from applyULSCounty beside it, and it is deliberate.
+// The automatic pass fills blanks only, because a value the operator or QRZ
+// supplied is usually better than one derived from a ZIP code. This one is asked
+// for by hand, on a chosen set of rows, precisely BECAUSE the stored county is
+// believed wrong — the Connecticut planning regions are the case that prompted
+// it: every CT contact logged before that correction holds a county the state
+// abolished in 2022, and no amount of filling blanks reaches them.
+//
+// Only US entities are touched, only callsigns the database knows, 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.
+func (a *App) UpdateQSOsCountyFromULS(ids []int64) (int, error) {
+	if a.qso == nil {
+		return 0, fmt.Errorf("db not initialized")
+	}
+	if a.uls == nil || a.uls.Count() == 0 {
+		return 0, fmt.Errorf("the US county database has not been downloaded yet — Settings › Awards › US counties")
+	}
+	changed := 0
+	for _, id := range ids {
+		q, err := a.qso.GetByID(a.ctx, id)
+		if err != nil || q.DXCC == nil {
+			continue
+		}
+		switch *q.DXCC {
+		case 291, 110, 6: // United States, Hawaii, Alaska
+		default:
+			continue
+		}
+		loc, ok := a.uls.Resolve(q.Callsign)
+		if !ok {
+			continue
+		}
+		cnty := loc.CNTY()
+		if cnty == "" {
+			continue
+		}
+		if q.County == cnty && (loc.State == "" || q.State == loc.State) {
+			continue
+		}
+		q.County = cnty
+		if loc.State != "" {
+			q.State = loc.State
+		}
+		if a.qso.Update(a.ctx, q) == nil {
+			changed++
+		}
+	}
+	if changed > 0 {
+		// The county IS the reference for CQ USA-CA and the state for WAS, so the
+		// stored award refs are stale the moment it changes.
+		a.invalidateAwardStats()
+		a.materializeAwardRefsForIDs(ids)
+	}
+	return changed, nil
+}
+
 // ULSStatusResult reports whether the county database is loaded, and how fresh.
 type ULSStatusResult struct {
 	Count     int    `json:"count"`