feat: store shard status in Redis

PluralKit.Core/Models/PKShardInfo.cs

@@ -1,18 +0,0 @@
-using NodaTime;
-
-namespace PluralKit.Core;
-
-public class PKShardInfo
-{
-    public enum ShardStatus
-    {
-        Down = 0,
-        Up = 1
-    }
-
-    public int Id { get; }
-    public ShardStatus Status { get; }
-    public float? Ping { get; }
-    public Instant? LastHeartbeat { get; }
-    public Instant? LastConnection { get; }
-}