chore: Improve script import mechanism and remove boilerplate

core/scripts/hysteria2/add_user.py

@@ -1,11 +1,11 @@
 #!/usr/bin/env python3
 
+import init_paths
 import sys
 import os
 import subprocess
 import re
 from datetime import datetime
-sys.path.append(os.path.join(os.path.dirname(__file__), '..'))
 from db.database import db
 
 def add_user(username, traffic_gb, expiration_days, password=None, creation_date=None, unlimited_user=False):