feat: ADIF monitor — auto-import QSOs from watched external ADIF files

Watches a configurable list of external ADIF files (fldigi RTTY logbook,
N1MM, VarAC…) and imports newly appended QSOs automatically. Each record
goes through the existing UDP-log path, so it gets full enrichment, ±2-minute
dedup (shared udpLogMu, can't race the UDP auto-log) and automatic upload to
the configured external services — no per-file toggles like Log4OM.

A newly added file starts at its current size (offset -1 sentinel → size on
first scan), so the QSOs already in it are NOT bulk-imported; only contacts
logged after it was added come in. Reads only up to the last complete <eor>
so a half-written record waits. Handles truncation/rotation (re-reads from 0,
dedup protects) and persists per-file offsets without clobbering a concurrent
UI edit of the file list.

New Settings → ADIF monitor section: master enable + add/remove/toggle files.
Backend emits adifmon:imported → the grid refreshes and a toast reports the
count. i18n EN + FR.

frontend/wailsjs/go/main/App.js

@@ -514,6 +514,10 @@ export function FlexTune(arg1) {
   return window['go']['main']['App']['FlexTune'](arg1);
 }
 
+export function GetADIFMonitor() {
+  return window['go']['main']['App']['GetADIFMonitor']();
+}
+
 export function GetActiveProfile() {
   return window['go']['main']['App']['GetActiveProfile']();
 }
@@ -1158,6 +1162,10 @@ export function PGXLSetFanMode(arg1) {
   return window['go']['main']['App']['PGXLSetFanMode'](arg1);
 }
 
+export function PickADIFMonitorFile() {
+  return window['go']['main']['App']['PickADIFMonitorFile']();
+}
+
 export function PickAudioFolder() {
   return window['go']['main']['App']['PickAudioFolder']();
 }
@@ -1338,6 +1346,10 @@ export function SaveADIFFile() {
   return window['go']['main']['App']['SaveADIFFile']();
 }
 
+export function SaveADIFMonitor(arg1) {
+  return window['go']['main']['App']['SaveADIFMonitor'](arg1);
+}
+
 export function SaveAlertRule(arg1) {
   return window['go']['main']['App']['SaveAlertRule'](arg1);
 }