feat: Added support for US Counties in OpsLog / Extra feature with DXHunter

internal/awardref/builtin.go

@@ -17,6 +17,7 @@ import (
 //   - WAC   → continent code ("EU", "NA", …)
 //   - WAS   → ADIF STATE code ("AL", …)
 //   - DDFM  → "D06" (the award pattern captures the leading D)
+//   - USCOUNTIES → canonical "STATE,COUNTY" key (see award.usCountyKey)
 func BuiltinRefs(code string) ([]Ref, bool) {
 	switch code {
 	case "DXCC":
@@ -29,6 +30,8 @@ func BuiltinRefs(code string) ([]Ref, bool) {
 		return usStates().Refs, true
 	case "DDFM":
 		return frenchDepartments(), true
+	case "USCOUNTIES":
+		return usCounties(), true
 	}
 	return nil, false
 }