feat(queue): implement concurrent deduplication and safe backend detachment

- Add backendRegisteredIds and backendDispatchPromises for single dispatch enforcement

- Add detach_download_for_reconfigure to safely modify properties of active downloads

- Add applyProperties logic handling completed, failed, paused, and active queues

- Add extractValidDownloadUrls and fix multi-url paste handling

- Setup vitest and add useDownloadStore unit tests for backend registration lifecycle

src/bindings/DownloadItem.ts

@@ -2,4 +2,4 @@
 import type { DownloadCategory } from "./DownloadCategory";
 import type { DownloadStatus } from "./DownloadStatus";
 
-export type DownloadItem = { id: string, url: string, fileName: string, status: DownloadStatus, fraction?: number, speed?: string, eta?: string, size?: string, category: DownloadCategory, dateAdded: string, connections?: number, speedLimit?: string, username?: string, password?: string, headers?: string, checksum?: string, cookies?: string, mirrors?: string, destination?: string, isMedia?: boolean, mediaFormatSelector?: string, queueId: string, };
+export type DownloadItem = { id: string, url: string, fileName: string, status: DownloadStatus, fraction?: number, speed?: string, eta?: string, size?: string, category: DownloadCategory, dateAdded: string, connections?: number, speedLimit?: string, username?: string, password?: string, headers?: string, checksum?: string, cookies?: string, mirrors?: string, destination?: string, isMedia?: boolean, mediaFormatSelector?: string, queueId: string, hasBeenDispatched?: boolean, };

src/bindings/EnqueueResult.ts

@@ -0,0 +1,3 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+
+export type EnqueueResult = { id: string, success: boolean, error?: string, };