refactor: restructure project into layered architecture

backend/app/db/session.py

@@ -1,11 +1,11 @@
 from sqlalchemy import create_engine
-from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import declarative_base
 from sqlalchemy.orm import sessionmaker
 
-DATABASE_URL = "sqlite:///./wheel.db"
+from config import settings
 
 engine = create_engine(
-    DATABASE_URL,
+    settings.DATABASE_URL,
     connect_args={"check_same_thread": False}
 )
 
@@ -15,13 +15,4 @@ SessionLocal = sessionmaker(
     bind=engine
 )
 
-# Database Session
-def get_db():
-    db = SessionLocal()
-
-    try:
-        yield db
-    finally:
-        db.close()
-        
 Base = declarative_base()