fix: the Yaesu keyer asked for a COM port it does not use

Selecting the Yaesu keyer fell through to the WinKeyer branch of the settings,
which offers a serial port picker and a Connect button. So the operator went
hunting for the right port — trying the standard COM and the enhanced one in turn
— and neither connected, because this keyer uses NEITHER: it keys over the CAT
link already configured in Settings → CAT.

It now has its own branch, like the Flex one: a speed field, the warning when the
CAT backend is not a Yaesu, and a line saying explicitly that keying rides the
CAT link. Speed changes go to the rig's keyer instead of a WinKeyer that is not
there.

frontend/src/App.tsx

@@ -38,7 +38,7 @@ import {
   ListCountries,
   GetWinkeyerSettings, SaveWinkeyerSettings, ListSerialPorts, GetWinkeyerStatus,
   WinkeyerConnect, WinkeyerDisconnect, WinkeyerSend, WinkeyerStop, WinkeyerSetSpeed, WinkeyerBackspace,
-  IcomSendCW, YaesuSendCW, YaesuStopCW, IcomStopCW, IcomSetKeySpeed, IcomSetBreakIn, GetIcomState,
+  IcomSendCW, YaesuSendCW, YaesuStopCW, SetYaesuKeySpeed, IcomStopCW, IcomSetKeySpeed, IcomSetBreakIn, GetIcomState,
   FlexSendCW, FlexStopCW, FlexSetKeySpeed, FlexBackspaceCW,
   GetDVKMessages, GetDVKStatus, DVKPlay, DVKStop,
   StartCWDecoder, StopCWDecoder, SetCWDecoderPitch,
@@ -5232,6 +5232,7 @@ export default function App() {
                   setWkWpm(w); saveWk({ wpm: w });
                   if (cwSource === 'icom') IcomSetKeySpeed(w).catch(() => {});
                   else if (cwSource === 'flex') FlexSetKeySpeed(w).catch(() => {});
+                  else if (cwSource === 'yaesu') SetYaesuKeySpeed(w).catch(() => {});
                   else WinkeyerSetSpeed(w).catch(() => {});
                 }}
                 onSend={wkSend}