Add tiered per-IP rate limiting to the router, completing the assembly:
- STRICT tier (~2 req/s, burst 20) on the unauthenticated, abuse-prone
surface: /api/v1/auth/* and /api/v1/website/*. This closes the
website-challenge growth vector (the prior rate-limit LOW): an unauthenticated
flood of challenge requests is now throttled per IP.
- NORMAL tier (~10 req/s, burst 60) on the authenticated wallet/identity API.
- PeerIpKeyExtractor keys on the peer IP; `main` now serves with
into_make_service_with_connect_info::<SocketAddr> so the IP is available, and
the test harness injects a loopback ConnectInfo (each test builds a fresh
router with fresh limiter state).
Over-limit returns 429. The limiter sits inside the global layers (CORS/timeout/
body/compression/trace) and in front of the handlers.
L1 test proves it throttles: a 40-request burst to a strict-tier route returns
429 (the governor runs before the handler, so even unauthenticated requests
count). All 33 integration tests + 114 lib tests pass through the fully-layered
router; openapi unchanged.
