Add Redis-backed cache backend with env switch

.env.development

@@ -20,3 +20,8 @@ KEYCLOAK_ADMIN_REALM=master
 PUBLIC_FRONTEND_ORIGINS=http://127.0.0.1:5173,http://localhost:5173
 INTERNAL_SHARED_SECRET=CHANGE_ME
 ADMIN_REQUIRED_GROUPS=member-admin
+
+CACHE_BACKEND=memory
+CACHE_REDIS_URL=redis://127.0.0.1:6379/0
+CACHE_PREFIX=memberapi
+CACHE_DEFAULT_TTL_SECONDS=30