chore: fix errenous windows paths from previous migration

packages/files/src/Domain/Device/FileBackupsDevice.ts

@@ -19,6 +19,8 @@ export interface FileBackupsDevice
     TextBackupsMethods {
   openLocation(path: string): Promise<void>
 
+  joinPaths(...paths: string[]): Promise<string>
+
   /**
    * The reason we combine presenting a directory picker and transfering old files to the new location
    * in one function is so we don't have to expose a general `transferDirectories` function to the web app,

packages/files/src/Domain/Service/BackupServiceInterface.ts

@@ -5,7 +5,7 @@ import { SuperConverterServiceInterface } from './SuperConverterServiceInterface
 
 export interface BackupServiceInterface {
   openAllDirectoriesContainingBackupFiles(): void
-  prependWorkspacePathForPath(path: string): string
+  prependWorkspacePathForPath(path: string): Promise<string>
   importWatchedDirectoryChanges(changes: DesktopWatchedDirectoriesChanges): Promise<void>
   setSuperConverter(converter: SuperConverterServiceInterface): void