Merge pull request #15142 from Classic298/fix-oauth

fix: OAuth authentication failure on second login due to stale session state

backend/open_webui/routers/auths.py

@@ -669,6 +669,7 @@ async def signup(request: Request, response: Response, form_data: SignupForm):
 @router.get("/signout")
 async def signout(request: Request, response: Response):
     response.delete_cookie("token")
+    response.delete_cookie("oui-session")
 
     if ENABLE_OAUTH_SIGNUP.value:
         oauth_id_token = request.cookies.get("oauth_id_token")