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/store/scanStore.ts

@@ -1,33 +0,0 @@
-import { create } from 'zustand';
-
-export type ScanPhase = 'idle' | 'starting' | 'running' | 'just-finished' | 'error';
-
-export interface ScanEntry {
-  phase: ScanPhase;
-  type: 'quick' | 'full';
-  count: number;
-  /** Set while user is in "press again to confirm" state for a full scan. */
-  confirmingFull: boolean;
-}
-
-const EMPTY: ScanEntry = { phase: 'idle', type: 'quick', count: 0, confirmingFull: false };
-
-interface ScanState {
-  byServer: Record<string, ScanEntry>;
-  get: (serverId: string) => ScanEntry;
-  set: (serverId: string, patch: Partial<ScanEntry>) => void;
-  clear: (serverId: string) => void;
-}
-
-export const useScanStore = create<ScanState>((set, getState) => ({
-  byServer: {},
-  get: (serverId) => getState().byServer[serverId] ?? EMPTY,
-  set: (serverId, patch) => set(s => ({
-    byServer: { ...s.byServer, [serverId]: { ...(s.byServer[serverId] ?? EMPTY), ...patch } },
-  })),
-  clear: (serverId) => set(s => {
-    const next = { ...s.byServer };
-    delete next[serverId];
-    return { byServer: next };
-  }),
-}));