fix: lazy-initialize DB engine in standalone scripts

Replace direct imports of `engine` and `SessionLocal` from `app.db.session`
with local instantiation via `get_database_url()` in create_db, insert_data,
and query_db scripts. Prevents DB connection attempts at import time when
environment variables are not yet loaded.

scripts/create_db.py

@@ -7,9 +7,11 @@ from dotenv import load_dotenv
 load_dotenv()
 
 from sqlalchemy import create_engine, text
-from app.db.session import engine
+from app.db.session import get_database_url
 from app.db.models import Base
 
+engine = create_engine(get_database_url())
+
 
 def create_database_if_not_exists():
     db_name = os.getenv("DB_NAME")

scripts/insert_data.py

@@ -7,7 +7,11 @@ from dotenv import load_dotenv
 load_dotenv()
 
 import pandas as pd
-from app.db.session import SessionLocal
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy import create_engine
+from app.db.session import get_database_url
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=create_engine(get_database_url()))
 from app.db.models import Employee
 from typing import cast, Any
 

scripts/query_db.py

@@ -7,7 +7,11 @@ from dotenv import load_dotenv
 load_dotenv()
 
 import pandas as pd
-from app.db.session import SessionLocal
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy import create_engine
+from app.db.session import get_database_url
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=create_engine(get_database_url()))
 from app.db.models import Employee, Prediction
 from app.routes.predict import _compute_features
 from ml_model.loader import load_pipeline