feat: added notification during fetching content ratings

Description

This MR shows notification when app lounge fetches content ratings for installed apps.

Screenshots

Technical details

Tests

Issues

backlog/-/issues/2203

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Summary by CodeRabbit

• New Features
  • Added notifications to inform users when content ratings for installed apps are being fetched.
  • Added a user-friendly message: "Gathering content rating for all the apps you've installed."