refactor(shellquote): replace go-shellquote with custom shell quoting implementation

core/playback/mpv/mpv.go

@@ -10,9 +10,9 @@ import (
 	"strings"
 	"sync"
 
-	"github.com/kballard/go-shellquote"
 	"github.com/navidrome/navidrome/conf"
 	"github.com/navidrome/navidrome/log"
+	"github.com/navidrome/navidrome/utils/shellquote"
 )
 
 func start(ctx context.Context, args []string) (Executor, error) {

core/playback/mpv/mpv_test.go

@@ -188,7 +188,7 @@ var _ = Describe("MPV", func() {
 
 			It("returns empty slice for empty template", func() {
 				args := createMPVCommand("auto", "/music/test.mp3", "/tmp/socket")
-				Expect(args).To(Equal([]string{}))
+				Expect(args).To(BeEmpty())
 			})
 		})
 	})