QBBB-FEAT-004 — Make vpnReady() truly fail-closed (verify bound IP equals the tunnel) — release-blocking

[itlezy]

Release-blocking per the WORKSPACE-POLICY Network Safety (no clearnet leak) P0 invariant. Spec: https://github.com/emulebb/qbittorrentbb/blob/master/docs/active/items/QBBB-FEAT-004.md