feat: Adds scheduler with wallclock timer (#2163)

### Summary

* Adds an event scheduler.
* Adds conveniences for hourly, daily, weekly, biweekly, monthly, ordinal monthly, and yearly recurrences

Example:

```cs
var tz = TimeZoneInfo.FindSystemTimeZoneById("America/New_York");

// Specify the time of the day, and the day of the week you want it to occur. Make sure it is translated into Utc.
// The next occurrence will be _after_ the specified date/time.
var scheduledEvent = EventScheduler.WeeklyAt(new DateTime(2025, 04, 26, 17, 00, 00), StartEvent, tz);

void StartEvent()
{
    World.Broadcast(0x30, false, "The event has started!");
}

Console.WriteLine("Event starts on {0}", scheduledEvent.NextOccurrence);
```

In this example, on _Saturday, May 3rd, 2025 @ 5pm ET_, the message "The event has started!" will be broadcasted.

Projects/Server/Utilities/Utility.cs

@@ -1468,4 +1468,21 @@ public static partial class Utility
         table.Remove(key);
         table.Add(key, value);
     }
+
+    public static DateTime LocalToUtc(this DateTime local, TimeZoneInfo tz)
+    {
+        if (tz.IsInvalidTime(local))
+        {
+            // For hourly recurrence, just subtract the standard offset (simulate as if the time exists)
+            return DateTime.SpecifyKind(local - tz.BaseUtcOffset, DateTimeKind.Utc);
+        }
+
+        if (tz.IsAmbiguousTime(local))
+        {
+            var offsets = tz.GetAmbiguousTimeOffsets(local);
+            return DateTime.SpecifyKind(local - offsets[1], DateTimeKind.Utc);
+        }
+
+        return DateTime.SpecifyKind(local - tz.GetUtcOffset(local), DateTimeKind.Utc);
+    }
 }