Add caching for MCSrvStat query requests to avoid rate limits

MCSrvStat is an external API used for querying Minecraft server data. Since it applies IP-based rate limits, frequent or repeated queries can trigger blocks. Add a caching mechanism for query mode responses to reduce request frequency.

The cache should have a configurable cooldown (in minutes) before new requests are sent, and the Multiplayer screen UI should display the last fetch time.