fix: populate app configs to system environment variables (#5590)

api/app.py

@@ -82,6 +82,16 @@ def create_flask_app_with_configs() -> Flask:
     """
     dify_app = DifyApp(__name__)
     dify_app.config.from_mapping(DifyConfig().model_dump())
+
+    # populate configs into system environment variables
+    for key, value in dify_app.config.items():
+        if isinstance(value, str):
+            os.environ[key] = value
+        elif isinstance(value, int | float | bool):
+            os.environ[key] = str(value)
+        elif value is None:
+            os.environ[key] = ''
+
     return dify_app