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.d.ts

@@ -278,6 +278,8 @@ export function FlexSetXITFreq(arg1:number):Promise<void>;
 
 export function FlexTune(arg1:boolean):Promise<void>;
 
+export function GetADIFMonitor():Promise<main.ADIFMonitorConfig>;
+
 export function GetActiveProfile():Promise<profile.Profile>;
 
 export function GetAlertEmailTo():Promise<string>;
@@ -600,6 +602,8 @@ export function OperatingDefaultForBand(arg1:string):Promise<operating.BandDefau
 
 export function PGXLSetFanMode(arg1:string):Promise<void>;
 
+export function PickADIFMonitorFile():Promise<string>;
+
 export function PickAudioFolder():Promise<string>;
 
 export function PickBackupFolder():Promise<string>;
@@ -690,6 +694,8 @@ export function RunBackupNow():Promise<string>;
 
 export function SaveADIFFile():Promise<string>;
 
+export function SaveADIFMonitor(arg1:main.ADIFMonitorConfig):Promise<void>;
+
 export function SaveAlertRule(arg1:alerts.Rule):Promise<alerts.Rule>;
 
 export function SaveAntGeniusSettings(arg1:main.AntGeniusSettings):Promise<void>;