feat(settings): add cover size settings and implement responsive cover sizing

Entire-Checkpoint: c2cea9c530e6

libs/shared/interfaces/src/lib/settings.interface.ts

@@ -18,6 +18,8 @@ export enum StartupBehavior {
     RestoreLastView = 'restore-last-view',
 }
 
+export type CoverSize = 'small' | 'medium' | 'large';
+
 /**
  * Describes all available settings options of the application
  */
@@ -39,4 +41,6 @@ export interface Settings {
     remoteControlPort: number;
     /** Custom download folder path (uses system Downloads folder if not set) */
     downloadFolder?: string;
+    /** Cover/poster sizing preset applied across grids and rails */
+    coverSize?: CoverSize;
 }