feat: SPE Expert amplifier control (serial/TCP) — OPERATE toggle + live status

Implements the SPE Application Programmer's Guide protocol: packets
0x55 0x55 0x55|CNT|DATA|CHK (sum%256), OPERATE key 0x0D (toggles STANDBY/OPERATE)
and STATUS request 0x90 whose 0xAA-framed reply is a 19-field CSV (mode, RX/TX,
band, power level, output W, SWR, V/I, temp, warnings, alarms). internal/spe
polls status ~1/s over USB serial (go.bug.st/serial, 8N1) or TCP (RS232-to-
Ethernet bridge) — same codec, different transport.

Wired via startPGXL (starts the SPE client for spe* types), bindings GetSPEStatus
/ SPESetOperate, and a live status card + OPERATE/STANDBY toggle in the Amplifier
settings panel. Only the two example-anchored commands are sent (safe); other
keystroke codes were ambiguous in the guide's table. Untested on hardware.

frontend/wailsjs/go/main/App.js

@@ -770,6 +770,10 @@ export function GetRotatorSettings() {
   return window['go']['main']['App']['GetRotatorSettings']();
 }
 
+export function GetSPEStatus() {
+  return window['go']['main']['App']['GetSPEStatus']();
+}
+
 export function GetSecretStatus() {
   return window['go']['main']['App']['GetSecretStatus']();
 }
@@ -1390,6 +1394,10 @@ export function RunBackupNow() {
   return window['go']['main']['App']['RunBackupNow']();
 }
 
+export function SPESetOperate(arg1) {
+  return window['go']['main']['App']['SPESetOperate'](arg1);
+}
+
 export function SaveADIFFile() {
   return window['go']['main']['App']['SaveADIFFile']();
 }