feat: enhance BackgroundImageSelector with custom image management

- Removed preserved custom URL handling and replaced it with a custom images array for better management of user-added backgrounds.
- Updated the component to allow adding, selecting, and removing custom images, improving user experience and flexibility.
- Adjusted background cycling logic to include custom images, ensuring a seamless integration with existing backgrounds.

src/lib/types.ts

@@ -107,6 +107,7 @@ export interface ViewPreferences {
   backgroundImage?: string;
   backgroundBlur?: number;
   backgroundOpacity?: number;
+  customImages?: string[];
   [key: string]:
     | boolean
     | 'tags'
@@ -117,6 +118,7 @@ export interface ViewPreferences {
     | 'large'
     | string
     | number
+    | string[]
     | undefined;
 }