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/en/settings.ts

@@ -473,16 +473,4 @@ export const settings = {
   floatingPlayerBarSub: 'Keep the player bar floating above content',
   uiScaleTitle: 'Interface Scale',
   uiScaleLabel: 'Zoom',
-  scan: {
-    quick: 'Quick scan',
-    full: 'Full scan',
-    quickTip: 'Quick scan — index new/changed files',
-    fullTip: 'Full scan — re-index everything',
-    confirmFull: 'Click again to confirm full scan',
-    confirmFullShort: 'Confirm full scan',
-    scanning: 'Scanning…',
-    done: 'Scan finished',
-    error: 'Scan failed',
-    toast: '{{name}}: scan finished — {{count}} tracks indexed',
-  },
 };