feat(quick-001): regenerate bindings and update frontend for multi-import

- Wails bindings reflect new PlaylistFilePicker and ImportPlaylists signatures
- Frontend handleImportPlaylist now passes file array to ImportPlaylists

frontend/wailsjs/go/frontendutil/FrontendUtil.d.ts

@@ -4,6 +4,6 @@ import {context} from '../models';
 
 export function DirectoryPicker():Promise<string>;
 
-export function PlaylistFilePicker():Promise<string>;
+export function PlaylistFilePicker():Promise<Array<string>>;
 
 export function SetContext(arg1:context.Context):Promise<void>;