Logout: redirect through federation sso-logout to clear all sessions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infrastructure/oauth.py

@@ -126,9 +126,7 @@ def create_oauth_blueprint(app_name: str) -> Blueprint:
         qsession.pop(SESSION_USER_KEY, None)
         qsession.pop("cart_sid", None)
         qsession.pop("sso_checked", None)
-        from shared.infrastructure.urls import blog_url
-        resp = redirect(blog_url("/"))
-        resp.delete_cookie("sso_hint", domain=".rose-ash.com", path="/")
-        return resp
+        # Redirect through federation to clear the SSO session too
+        return redirect(federation_url("/auth/sso-logout/"))
 
     return bp