This commit enhances the Radio France source by:
1. Updating the main.rs file to clarify the purpose of registering the Radio France source, including API route initialization
2. Modifying sources.rs to:
- Add RadioFranceExt to the imports
- Initialize API routes for Radio France after registering the source
3. Updating source.rs to:
- Use a default logo for Radio France containers when server_base_url is configured
- Apply the default logo to both group and 'Radios ICI' containers
These changes improve the integration and visual presentation of Radio France content within the media server.