Wrap blocking mkdir() calls in run_blocking for async startup and setup

backend/app/services/setup_service.py

@@ -175,7 +175,7 @@ async def _ensure_database_initialized(database_path: str) -> bool:
     parent_dir = database_path_obj.parent
 
     try:
-        parent_dir.mkdir(parents=True, exist_ok=True)
+        await run_blocking(parent_dir.mkdir, parents=True, exist_ok=True)
     except PermissionError:
         log.warning(
             "cannot_create_runtime_database_parent",

backend/app/startup.py

@@ -70,7 +70,7 @@ async def startup_shared_resources(
         A tuple of ``(http_session, scheduler)``.
     """
     db_path: Path = Path(settings.database_path)
-    db_path.parent.mkdir(parents=True, exist_ok=True)
+    await run_blocking(db_path.parent.mkdir, parents=True, exist_ok=True)
 
     log.debug("database_directory_ensured", directory=str(db_path.parent))