Refactor ESLint configuration and update code formatting: Standardize quotes in eslint.config.mjs, next.config.js, and various TypeScript files for consistency. Add Prettier as a dependency and include formatting scripts in package.json. Clean up unnecessary whitespace in multiple files to enhance code readability.

lib/auth.ts

@@ -68,4 +68,3 @@ export const { handlers, signIn, signOut, auth } = NextAuth({
     strategy: "jwt",
   },
 });
-

lib/preferences.ts

@@ -22,4 +22,3 @@ export async function getBackgroundImage(
     return defaultImage;
   }
 }
-