Standardize async offloading behind shared executor helper

backend/app/services/setup_service.py

@@ -8,6 +8,7 @@ enforcing the rule that setup can only run once.
 from __future__ import annotations
 
 import asyncio
+from app.utils.async_utils import run_blocking
 from pathlib import Path
 from typing import TYPE_CHECKING
 
@@ -82,8 +83,8 @@ async def run_setup(
     # the asyncio event loop.
     password_bytes = master_password.encode()
     loop = asyncio.get_running_loop()
-    hashed: str = await loop.run_in_executor(
-        None, lambda: bcrypt.hashpw(password_bytes, bcrypt.gensalt()).decode()
+    hashed: str = await run_blocking(
+        lambda: bcrypt.hashpw(password_bytes, bcrypt.gensalt()).decode()
     )
 
     await settings_repo.set_setting(db, _KEY_PASSWORD_HASH, hashed)