Next.js WebSocket upgrade SSRF (CVE-2026-44578) detection

Detects Next.js and flags CVE-2026-44578 router-server WebSocket upgrade SSRF. Affected: 13.4.13–15.5.15 and 16.0.0–16.2.4; fixed in 15.5.16 / 16.2.5. Self-hosted Node server only Vercel not affected. Optional active probe: absolute-URI WebSocket upgrade to AWS IMDSv1. Companion auxiliary confirm...