Replaces raw string queries with structured `SearchQuery` types across the `MusicSource` trait and UPnP handlers. Adds dedicated paginated endpoints, explicit caching, and type-specific filtering for the Qobuz source. Fixes a frontend navigation bug by aligning state management with UPnP browse semantics and properly routing virtual container IDs. Also updates the Makefile for dynamic `RUST_LOG` configuration, standardizes logging with `tracing`, and adds the dependency lockfile.
