feat: add metadata-agregator gRPC client integration

- Add tonic/prost for gRPC client generation
- Add proto definitions from metadata-agregator service
- Add MetadataClient and MetadataService for gRPC communication
- Add REST controller exposing metadata endpoints (search, get, sync)
- Update config with metadata.endpoint setting
- Update flake.nix with protobuf for proto compilation

src/main.rs

@@ -4,7 +4,7 @@ use tokio::sync::RwLock;
 use axum::Router;
 use music_agregator::{
     api, config,
-    services::{IndexerService, TorrentService},
+    services::{IndexerService, MetadataService, TorrentService},
     AppServices, AppState,
 };
 use tower_http::cors::{Any, CorsLayer};
@@ -60,9 +60,26 @@ async fn main() {
         TorrentService::new()
     };
 
+    let mut metadata_service = MetadataService::new(&config.metadata.endpoint);
+    match metadata_service.connect().await {
+        Ok(()) => {
+            tracing::info!(
+                "connected to metadata service at {}",
+                config.metadata.endpoint
+            );
+        }
+        Err(e) => {
+            tracing::warn!(
+                "failed to connect to metadata service: {} (continuing without metadata)",
+                e
+            );
+        }
+    }
+
     let state: AppState = Arc::new(RwLock::new(AppServices::new(
         indexer_service,
         torrent_service,
+        metadata_service,
     )));
 
     let cors = CorsLayer::new()