feat: ESM (Enter Sends Message) for CW keyers, N1MM-style

With ESM enabled (Settings → CW Keyer), the keyer active and mode CW, Enter in
the entry strip fires a macro by QSO stage instead of logging:
- callsign field empty            → F1 (CQ)
- callsign entered (in call field) → F2 (report), then focus jumps to RST-sent
- Enter in RST-sent / RST-rcvd     → F3 (TU), which logs via its own <LOGQSO>

Works for every keyer engine (WinKeyer / serial DTR-RTS / Flex CWX / Icom CI-V)
since it routes through the shared macro sender. Enter in other fields still logs
normally, and ESM off keeps the classic Enter-to-log behaviour.

Backend: new `esm` flag on WinkeyerSettings (winkeyer.esm). Frontend: esmHandleEnter
state machine keyed off data-esm markers on the call/RST blocks, a Settings
checkbox + hint, and i18n EN/FR.

frontend/wailsjs/go/models.ts

@@ -3085,6 +3085,7 @@ export namespace main {
 	    engine: string;
 	    esc_clears_call: boolean;
 	    send_on_type: boolean;
+	    esm: boolean;
 	    macros: WKMacro[];
 	
 	    static createFrom(source: any = {}) {
@@ -3114,6 +3115,7 @@ export namespace main {
 	        this.engine = source["engine"];
 	        this.esc_clears_call = source["esc_clears_call"];
 	        this.send_on_type = source["send_on_type"];
+	        this.esm = source["esm"];
 	        this.macros = this.convertValues(source["macros"], WKMacro);
 	    }