fix(adif): a logged QSO carries its receive side

The importer has always read an absent BAND_RX/FREQ_RX as 'not split, so
RX = TX'. The logging paths never did, so what a contact carried
depended on which door it came in through — and it shows outside
OpsLog: the record forwarded over UDP is written from the QSO as logged,
so a receiver that reads BAND_RX (Log4OM does) found nothing there.

Filled at AddQSO, the one funnel every path goes through, so the
database, the export and the forwarded copy agree. A genuine split
contact keeps what it was given — table-tested both ways.

app.go

@@ -2948,6 +2948,28 @@ func (a *App) reloadLookupProviders() {
 
 // --- QSO bindings ---
 
+// fillRXDefaults stamps the receive side when the contact was not split.
+//
+// The ADIF importer has always done this — an absent BAND_RX/FREQ_RX means RX
+// equals TX — but the LOGGING paths did not, so what a QSO carried depended on
+// which door it came through. It shows up outside OpsLog: the record forwarded
+// to another logger over UDP is written from the QSO as logged, and a receiver
+// reading BAND_RX (Log4OM does) found nothing there for contacts logged by a
+// path that left it blank.
+//
+// Applied at AddQSO, the one funnel every path goes through — manual entry, the
+// WSJT-X/UDP log, CW, contest, net control, the ADIF monitor — so the database,
+// the export and the forwarded copy all say the same thing.
+func fillRXDefaults(q *qso.QSO) {
+	if strings.TrimSpace(q.BandRX) == "" {
+		q.BandRX = q.Band
+	}
+	if q.FreqRXHz == nil && q.FreqHz != nil {
+		v := *q.FreqHz
+		q.FreqRXHz = &v
+	}
+}
+
 func (a *App) AddQSO(q qso.QSO) (id int64, err error) {
 	if a.qso == nil {
 		return 0, fmt.Errorf("db not initialized")
@@ -2963,6 +2985,7 @@ func (a *App) AddQSO(q qso.QSO) (id int64, err error) {
 		}
 	}()
 	a.applyStationDefaults(&q, true)
+	fillRXDefaults(&q)
 	fillDistance(&q)
 	a.applyDXCCNumber(&q)
 	a.applyULSCounty(&q)               // fill blank US county/grid from the offline ULS store