Sort packages by availability and tidy availability-related displays

- Make the Verfügbarkeit column sortable from fully online through partial and unchecked down to fully offline, reversing on the second click
- Show partially available packages in the warning color as soon as one link is online and one is offline
- Switch the package order instantly on column sorts instead of sliding rows
- Keep offline links out of the package status error count
- Show queue volumes of one terabyte or more as grouped gigabytes with one decimal per language

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MxAH7rSv8MgfKEPwMkR8N2

src/renderer/views/downloads/DownloadsView.tsx

@@ -52,6 +52,7 @@ export interface DownloadsViewModel extends DownloadsViewModelCore {
   gridTemplate: string;
   sortColumn?: DownloadSortColumn;
   sortDirection?: "asc" | "desc";
+  packageOrderSortRevision?: number;
   disclosureRevision: number;
   animationsEnabled: boolean;
   status: DownloadsStatusModel;