feat(security): add Memcached-based rate limiting for remember-token auto-login

Prevents brute-force attacks against remember-me cookies. Uses Memcached
(Cache::add + increment) to track failures per IP: 5 attempts in 15 min
window, auto-expiring via TTL. Counter resets on successful auto-login.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/Service/Auth/AuthServicesFactory.php

@@ -80,7 +80,8 @@ class AuthServicesFactory
             $this->sessionStore,
             $this->cookieStore,
             $this->requestRuntime,
-            $this->authGatewayFactory->createAuthSettingsGateway()
+            $this->authGatewayFactory->createAuthSettingsGateway(),
+            new RememberMeRateLimiter()
         );
     }