chore(servers): remove quick/full scan buttons from server cards (#843)

Drops the Quick/Full scan actions and all supporting logic — they are no
longer needed. Removes the ServerScanActions component (incl. the unused
compact variant), the subsonicScan API, the scanStore, and the app-root
useScanPolling hook (no more background scan polling). Cleans up the
.server-scan-* CSS and the settings.scan i18n block across all 9 locales.

440 deletions, no new code; tsc + bundle clean.

src/locales/nb/settings.ts

@@ -467,16 +467,4 @@ export const settings = {
   floatingPlayerBarSub: 'Hold spillerlinjen flytende over innholdet',
   uiScaleTitle: 'Grensesnittskala',
   uiScaleLabel: 'Zoom',
-  scan: {
-    quick: 'Hurtigskanning',
-    full: 'Full skanning',
-    quickTip: 'Hurtigskanning — indekser nye/endrede filer',
-    fullTip: 'Full skanning — reindekser alt',
-    confirmFull: 'Klikk igjen for å bekrefte',
-    confirmFullShort: 'Bekreft full skanning',
-    scanning: 'Skanner…',
-    done: 'Skanning ferdig',
-    error: 'Skanning mislyktes',
-    toast: '{{name}}: skanning ferdig — {{count}} spor indeksert',
-  },
 };