refactor(logging): move logging setup to internal/logging

Moves logging configuration and setup to a dedicated package. Updates Config struct to use nested LoggingConfig. Updates main.go to use the new logging package.

cmd/app/main.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/placeholder/golang-template/internal/config"
+	"github.com/placeholder/golang-template/internal/logging"
 )
 
 func main() {
@@ -27,11 +28,9 @@ func main() {
 	}
 
 	// Setup Logger
-	opts := &slog.HandlerOptions{
-		Level: config.ParseLogLevel(cfg.LogLevel),
-	}
-	logger := slog.New(slog.NewJSONHandler(os.Stdout, opts))
-	slog.SetDefault(logger)
+	logging.Configure(logging.Config{
+		Level: cfg.Logging.Level,
+	})
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()