feat(albums): add multi-select to Albums, New Releases, and Random Albums

Select multiple albums to add them to the offline cache or download
each as a separate ZIP. Action buttons appear inline in the topbar
when at least one album is selected; title shows selection count.
AlbumCard gains selectionMode/selected/onToggleSelect props with a
checkmark overlay and selected outline.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/locales/de.ts

@@ -244,6 +244,17 @@ export const deTranslation = {
     yearTo: 'Bis',
     yearFilterClear: 'Jahresfilter zurücksetzen',
     yearFilterLabel: 'Jahr',
+    select: 'Mehrfachauswahl',
+    startSelect: 'Mehrfachauswahl aktivieren',
+    cancelSelect: 'Abbrechen',
+    selectionCount: '{{count}} ausgewählt',
+    downloadZips: 'ZIPs herunterladen',
+    addOffline: 'Offline hinzufügen',
+    downloadingZip: 'Lade {{current}}/{{total}} herunter: {{name}}',
+    downloadZipDone: '{{count}} ZIP(s) heruntergeladen',
+    downloadZipFailed: 'Download fehlgeschlagen: {{name}}',
+    offlineQueuing: '{{count}} Album(s) für Offline einreihen…',
+    offlineFailed: '{{name}} konnte nicht offline hinzugefügt werden',
   },
   artists: {
     title: 'Künstler',