feat(device-sync): manifest, cancel, font picker + sync status fix

- Write psysonic-sync.json to device after sync/deletions; auto-import
  on folder select when localStorage is empty (cross-platform handoff)
- Add cancel button during active sync: AtomicBool flag per job,
  tasks bail after acquiring semaphore, cancelled state in UI
- Fix sync status staying "pending": normalize template path separators
  to OS separator (Windows: '/' → '\') so compute_sync_paths and
  list_device_dir_files produce matching strings for Set comparison
- Add Geist and JetBrains Mono as variable fonts; font picker collapsible
- Fix device mount detection on Windows: removable drive letters (E:\)
  were incorrectly skipped alongside system roots; strip \?\ prefix
  from canonicalized paths before mount-point comparison

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

src/locales/ru.ts

@@ -1156,6 +1156,8 @@ export const ruTranslation = {
     fetchError: 'Ошибка загрузки треков с сервера.',
     syncComplete: 'Синхронизация завершена.',
     dismiss: 'Закрыть',
+    cancelSync: 'Отмена',
+    syncCancelled: 'Синхронизация отменена ({{done}} / {{total}} перенесено).',
     colName: 'Название',
     colType: 'Тип',
     colStatus: 'Статус',
@@ -1165,6 +1167,7 @@ export const ruTranslation = {
     deleteFromDevice: 'Пометить для удаления ({{count}})',
     confirmDelete: 'Удалить {{count}} запись(ей) с устройства: {{names}}?',
     deleteComplete: '{{count}} запись(ей) удалено с устройства.',
+    manifestImported: 'Импортировано {{count}} источник(ов) из манифеста устройства.',
     statusSynced: 'Синхронизировано',
     statusPending: 'Ожидает',
     statusDeletion: 'Удаление',