Add a MOTD feature

Cette issue n'a pas de description.

The issue body is empty, so the first step is to understand what a MOTD (Message of the Day) feature entails for a game launcher. Look at the existing codebase for UI components and configuration loading, likely in src/ directory. Check how other features like game listing or settings are implemented to see where MOTD data could be fetched and displayed. Determine if it's a network call, a local file, or a static message, and where in the Tauri frontend (React) it should appear.

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