EdgeZero migration Phase 4 — Handlers to extractors

[aram356]

Part of #840. Spec: docs/superpowers/specs/2026-07-02-edgezero-full-migration-design.md §5 Phase 4. Depends on edgezero Phase 0 (State<T>); cleaner after Phase 1 (#841).

Rewrite core handle_* (proxy, publisher, auction/endpoints, request_signing/endpoints, ec/*) to #[action] + FromRequest extractors using State<...> and store extractors. Delete per-adapter handler shims + NamedRouteHandler enums; retire RuntimeServices. EC lifecycle/pre-route filters stay as middleware. Phase 4b (optional): integration proxy router.
Acceptance: all named routes served via #[action]; parity green.