fix(redis): add maintenance notification startup switch

Default Redis maintenance notification negotiation to disabled and apply the startup-only setting to both platform and Asynq clients.

.env.example

@@ -49,6 +49,8 @@ REDIS_ADDR=redis:6379
 # REDIS_DB=0
 REDIS_KEY_PREFIX=openflare:
 # REDIS_POOL_SIZE=100
+# 启动时开关；修改后需重启服务
+REDIS_MAINT_NOTIFICATIONS=false
 # compose 宿主机映射端口（仅 docker-compose 使用）
 # REDIS_PORT=6379