feat: add SongSearchService and GET /songs?q= search endpoint

crates/common/src/lib.rs

@@ -1,4 +1,4 @@
-use domain::{RepositoryError, Song, SongRepositoryPort, SongSummary, StoredSong};
+use domain::{RepositoryError, Song, SongRepositoryPort, SongSearchPort, SongSummary, StoredSong};
 use uuid::Uuid;
 
 pub struct SongService {
@@ -26,3 +26,17 @@ impl SongService {
         self.repo.delete(id).await
     }
 }
+
+pub struct SongSearchService {
+    search: Box<dyn SongSearchPort>,
+}
+
+impl SongSearchService {
+    pub fn new(search: Box<dyn SongSearchPort>) -> Self {
+        Self { search }
+    }
+
+    pub async fn search(&self, query: &str) -> Result<Vec<domain::SongSummary>, domain::RepositoryError> {
+        self.search.search(query).await
+    }
+}