Add TNEF handling and email loading improvements

- Implement TNEF extraction and recursive parsing in new `tnef_reader.go` and associated tests.
- Create tests for TNEF extraction scenarios in `tnef_diag_test.go`, `tnef_diag7_test.go`, and `tnef_diag8_test.go`.

frontend/src/lib/wailsjs/go/main/App.d.ts

@@ -1,15 +1,29 @@
 // Cynhyrchwyd y ffeil hon yn awtomatig. PEIDIWCH Â MODIWL
 // This file is automatically generated. DO NOT EDIT
-import {utils} from '../models';
 import {main} from '../models';
+import {utils} from '../models';
 import {internal} from '../models';
 
+export function CheckForUpdates():Promise<main.UpdateStatus>;
+
 export function CheckIsDefaultEMLHandler():Promise<boolean>;
 
+export function ConvertToUTF8(arg1:string):Promise<string>;
+
+export function CreateBugReportFolder():Promise<main.BugReportResult>;
+
+export function DetectEmailFormat(arg1:string):Promise<string>;
+
+export function DownloadUpdate():Promise<string>;
+
+export function ExportSettings(arg1:string):Promise<string>;
+
 export function FrontendLog(arg1:string,arg2:string):Promise<void>;
 
 export function GetConfig():Promise<utils.Config>;
 
+export function GetCurrentMailFilePath():Promise<string>;
+
 export function GetImageViewerData():Promise<main.ImageViewerData>;
 
 export function GetMachineData():Promise<utils.MachineInfo>;
@@ -18,14 +32,26 @@ export function GetPDFViewerData():Promise<main.PDFViewerData>;
 
 export function GetStartupFile():Promise<string>;
 
+export function GetUpdateStatus():Promise<main.UpdateStatus>;
+
 export function GetViewerData():Promise<main.ViewerData>;
 
+export function ImportSettings():Promise<string>;
+
+export function InstallUpdate(arg1:boolean):Promise<void>;
+
+export function InstallUpdateSilent():Promise<void>;
+
+export function InstallUpdateSilentFromPath(arg1:string):Promise<void>;
+
 export function IsDebuggerRunning():Promise<boolean>;
 
 export function OpenDefaultAppsSettings():Promise<void>;
 
 export function OpenEMLWindow(arg1:string,arg2:string):Promise<void>;
 
+export function OpenFolderInExplorer(arg1:string):Promise<void>;
+
 export function OpenImage(arg1:string,arg2:string):Promise<void>;
 
 export function OpenImageWindow(arg1:string,arg2:string):Promise<void>;
@@ -34,8 +60,12 @@ export function OpenPDF(arg1:string,arg2:string):Promise<void>;
 
 export function OpenPDFWindow(arg1:string,arg2:string):Promise<void>;
 
+export function OpenURLInBrowser(arg1:string):Promise<void>;
+
 export function QuitApp():Promise<void>;
 
+export function ReadAuto(arg1:string):Promise<internal.EmailData>;
+
 export function ReadEML(arg1:string):Promise<internal.EmailData>;
 
 export function ReadMSG(arg1:string,arg2:boolean):Promise<internal.EmailData>;
@@ -46,4 +76,16 @@ export function ReadPEC(arg1:string):Promise<internal.EmailData>;
 
 export function SaveConfig(arg1:utils.Config):Promise<void>;
 
+export function SaveScreenshot():Promise<string>;
+
+export function SaveScreenshotAs():Promise<string>;
+
+export function SetCurrentMailFilePath(arg1:string):Promise<void>;
+
+export function SetUpdateCheckerEnabled(arg1:boolean):Promise<void>;
+
 export function ShowOpenFileDialog():Promise<string>;
+
+export function SubmitBugReport(arg1:main.BugReportInput):Promise<main.SubmitBugReportResult>;
+
+export function TakeScreenshot():Promise<main.ScreenshotResult>;