chore(providers): remove a keyless provider integration at its operator's request (#12440)

The service operator asked in writing (2026-08-30) that their service be
removed from OmniRoute entirely: executor, registry entry, no-auth catalog
entry and alias, icon mapping, env var, docs rows, dedicated tests and
snapshots, and every passing mention in comments, fixtures and CHANGELOG
entries. Provider count drops from 355 to 354 on every canonical surface.

Co-authored-by: Markus Hartung <diegosouzapw@users.noreply.github.com>