refactor: remove db package and move database logic to service layer

cmd/init.go

@@ -1,8 +1,8 @@
 package cmd
 
 import (
-	"axolotl/db"
 	"axolotl/output"
+	"axolotl/service"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -22,7 +22,7 @@ var initCmd = &cobra.Command{
 			fmt.Fprintln(os.Stderr, "database already exists:", dbPath)
 			os.Exit(1)
 		}
-		if err := db.Init(dbPath); err != nil {
+		if err := service.InitNodeService(dbPath); err != nil {
 			fmt.Fprintln(os.Stderr, "failed to initialize:", err)
 			os.Exit(1)
 		}