fix(wavelog): send v2 extra freq fields as MHz strings with unit suffix

WaveLog's parse_frequency() (Logbook_model.php) treats integer input
as Hz but reads string suffixes ("145.852038M" -> 145852038 Hz).
The bare-integer freq/freq_rx values in the v2 JSON envelope could be
misread as MHz by older WaveLog versions, corrupting the band
derivation (145.852 MHz showed up as 160m). ADIF string (v1/v2) was
already correct; now the extra fields match the same semantics.

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/wavelog/WaveLogApi.kt

@@ -149,8 +149,8 @@ object WaveLogApi {
             put("mode", qso.mode)
             put("qso_date", utcDate(qso.timeUtcMs))
             put("time_on", utcTime(qso.timeUtcMs))
-            put("freq", qso.freqTxHz)
-            put("freq_rx", qso.freqRxHz)
+            put("freq", String.format(Locale.ENGLISH, "%.6fM", qso.freqTxHz / 1_000_000.0))
+            put("freq_rx", String.format(Locale.ENGLISH, "%.6fM", qso.freqRxHz / 1_000_000.0))
             put("gridsquare", gridsquare)
             put("rst_sent", "59")
             put("rst_rcvd", "59")