Bump undici to ^6.23.1 via overrides — patches GHSA-g9mf-h72j-4rw9, GHSA-2mjp-6q6p-2qxm, GHSA-vrm6-8vpv-qv8q, GHSA-v9p9-hfj2-hcw8, GHSA-4992-7rv2-5pvq (5 advisories: smuggling, memory exhaustion, CRLF injection, WebSocket DoS). Smoke-tested: action reaches the API and handles the response correctly.

Author: rajibcse94