GHSA-45PQ-889G-FCGH rclone: Incomplete path validation allows backend root escape in serve restic

Summary rclone serve restic does not correctly reject URL paths beginning with ../. On affected backends, an attacker who can access the REST endpoint can read, create, overwrite, or delete objects outside the path configured by the operator. The issue affects rclone v1.40 through rclone v1.74.4...