Give the debug-to-file recording a home in the Compose settings

origin/main added a checkbox to the old JavaFX settings that recorded the whole
ON4KST session to file; the Compose redraw dropped the old settings UI, so the
toggle had no control left even though the preference and its wiring survived
the rebase.

It returns to the message-handling tab: the state writes the preference and asks
the application, through a new SettingsHost callback, to open or close the
error-log handler and the history recorder in the order the old checkbox kept.
The explanatory line and its German translation say that passwords are redacted.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app-desktop/src/main/i18n/strings_en.properties

@@ -76,6 +76,9 @@ messageHandling.autoAnswerSection=Automatic answer to private messages
 messageHandling.autoAnswerText=Answer text
 messageHandling.qrgAnswerEnabled=Answer a QRG request with the current frequency
 messageHandling.qrgAnswerSection=Automatic answer to a QRG request
+messageHandling.debugToFileEnabled=Record the whole session to file
+messageHandling.debugToFileHint=Records complete ON4KST RX/TX session traffic in Messagehistory.raw and adds diagnostic details to kst4contest-errors.log. Login passwords are redacted. Warnings and errors are always logged.
+messageHandling.diagnosticsSection=Diagnostics
 notification.addCallsignToList=Add a callsign to the monitoring list
 notification.addMonitored=Add monitored callsign
 notification.bandUpgradeHint=Hint at a band upgrade when a QSO is logged