Fix connect args for PostgreSQL

Author: orabe

backend/app/database.py

@@ -4,16 +4,30 @@
 
 DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///./certificates.db")
 
-# Adjust connection arguments for SQLite only
-connect_args = {"check_same_thread": False} if DATABASE_URL.startswith("sqlite") else None
+# SQLite needs check_same_thread=False.
+# PostgreSQL does not need extra connect_args.
+connect_args = {}
+
+if DATABASE_URL.startswith("sqlite"):
+    connect_args = {"check_same_thread": False}
+
+engine = create_engine(
+    DATABASE_URL,
+    connect_args=connect_args,
+)
+
+SessionLocal = sessionmaker(
+    autocommit=False,
+    autoflush=False,
+    bind=engine,
+)
 
-engine = create_engine(DATABASE_URL, connect_args=connect_args)
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 Base = declarative_base()
 
+
 def get_db():
     db = SessionLocal()
     try:
         yield db
     finally:
-        db.close()
+        db.close()