Add missing os import

Fixes #4042

Author: vsantele

src/promptflow-core/CHANGELOG.md

@@ -1,5 +1,11 @@
 # promptflow-core package
 
+## Unreleased
+
+### Bugs fixed
+
+- Added missing `os` import in `static_web_blueprint.py` ([#4042](https://github.com/microsoft/promptflow/issues/4042)).
+
 ## v1.18.1 (2025.6.10)
 
 ### Bugs fixed

src/promptflow-core/promptflow/core/_serving/v1/blueprint/static_web_blueprint.py

@@ -1,7 +1,7 @@
 # ---------------------------------------------------------
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # ---------------------------------------------------------
-
+import os
 from pathlib import Path
 
 import flask