Enhance Radio France source with API routes initialization and default album art

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.

pmomediaserver/src/sources.rs

@@ -243,7 +243,7 @@ impl SourcesExt for Server {
 
     #[cfg(feature = "radiofrance")]
     async fn register_radiofrance(&mut self) -> Result<()> {
-        use pmoradiofrance::{RadioFranceSource, RadioFranceStatefulClient};
+        use pmoradiofrance::{RadioFranceExt, RadioFranceSource, RadioFranceStatefulClient};
 
         tracing::info!("Initializing Radio France source...");
 
@@ -265,6 +265,11 @@ impl SourcesExt for Server {
         // Enregistrer la source
         self.register_music_source(Arc::new(source)).await;
 
+        // Initialiser les routes API Radio France
+        self.init_radiofrance().await.map_err(|e| {
+            SourceInitError::RadioFranceError(format!("Failed to init API routes: {}", e))
+        })?;
+
         tracing::info!("✅ Radio France source registered successfully");
 
         Ok(())