refactor: zoom a livello di dispositivo e rimozione zoom da playlist

src/app/services/settings.service.ts

@@ -59,6 +59,9 @@ export class SettingsService {
   /** Schermo nero per l'ascolto delle playlist in macchina: true = attivo */
   public carModeBlackScreen = signal<boolean>(false);
 
+  /** Global zoom/font size factor for song presentation */
+  public globalZoom = signal<number>(1.0);
+
   /** Identificativo utente univoco per la gestione delle comunità */
   public userUuid = signal<string>('');
 
@@ -264,6 +267,14 @@ export class SettingsService {
       this.carModeBlackScreen.set(false);
     }
 
+    const savedGlobalZoom = localStorage.getItem('global-zoom');
+    if (savedGlobalZoom !== null) {
+      const parsed = parseFloat(savedGlobalZoom);
+      this.globalZoom.set(isNaN(parsed) ? 1.0 : parsed);
+    } else {
+      this.globalZoom.set(1.0);
+    }
+
     // Sync browser fullscreen state with listeners (supporting vendor prefixes)
     const updateFullscreenState = () => {
       const isFs = !!(
@@ -325,6 +336,10 @@ export class SettingsService {
       localStorage.setItem('car-mode-black-screen', this.carModeBlackScreen().toString());
     });
 
+    effect(() => {
+      localStorage.setItem('global-zoom', this.globalZoom().toString());
+    });
+
     effect(() => {
       const active = this.keepScreenOn();
       localStorage.setItem('keep-screen-on', active.toString());