feat: store timeouts in database and log them ending

we have to do this because discord doesn't notify us when a timeout
ends naturally, only when a moderator removes it early.

Catalogger.Backend/Database/Models/DiscordTimeout.cs

@@ -0,0 +1,12 @@
+using NodaTime;
+
+namespace Catalogger.Backend.Database.Models;
+
+public class DiscordTimeout
+{
+    public int Id { get; init; }
+    public ulong UserId { get; init; }
+    public ulong GuildId { get; init; }
+    public ulong? ModeratorId { get; init; }
+    public Instant Until { get; init; }
+}