feat(icom): a DATA button, native PSK, real watts — and the audio codec

The console gains a DATA mode button (USB-D, what FT8 and friends ride on);
the PSK button now maps to the rigs' native PSK mode (0x12) instead of erroring
as an unknown mode — rigs without one NAK it, exactly as RS-BA1's button does
there. The power meter shows real watts on the IC-7760, whose meter face runs
to 250 W where a 100 W rig's percentage was the watts. The clickable S-meter
gets a pointer cursor so it looks like what it is.

Network audio: rxcodec 0x04 — the experiments on the real 7760 settle the
codec table (0x10 = 16-bit stereo, 0x02 = 8-bit mono, both heard as garble),
and 0x04 is the 16-bit mono the playback path actually plays.

internal/cat/icomserial.go

@@ -1494,6 +1494,12 @@ func (b *IcomSerial) modeCode(mode string) (code byte, data bool, err error) {
 		return civ.ModeFM, false, nil
 	case "RTTY", "FSK":
 		return civ.ModeRTTY, false, nil
+	case "PSK":
+		// The console button, not the ADIF mode: the rigs that HAVE a native PSK
+		// mode (7610/7760/7851 class) get it; a 7300 NAKs 0x12 and the button
+		// stays dead there, exactly as RS-BA1's does. Soundcard PSK31 stays on
+		// USB-D below, where every rig can do it.
+		return civ.ModePSK, false, nil
 	case "FT8", "FT4", "PSK31", "MFSK", "JS8", "JT65", "JT9", "OLIVIA", "DATA", "DIGITALVOICE":
 		// Digital data modes ride on USB with the data flag set (FT8 etc.).
 		return civ.ModeUSB, true, nil