feat(CS-P1): Castle Siege phase state machine (in-memory, time-injected) + tests

src/GameLogic/CastleSiege/CastleSiegePhase.cs

@@ -0,0 +1,26 @@
+// <copyright file="CastleSiegePhase.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.GameLogic.CastleSiege;
+
+/// <summary>
+/// The phases of a Castle Siege cycle.
+/// </summary>
+public enum CastleSiegePhase
+{
+    /// <summary>Resting phase: castle is (un)owned, waiting for the next registration window.</summary>
+    Ownership,
+
+    /// <summary>Guilds can register to attack.</summary>
+    Registration,
+
+    /// <summary>Registration closed; defenders prepare before the siege starts.</summary>
+    Preparation,
+
+    /// <summary>The siege battle is running.</summary>
+    Siege,
+
+    /// <summary>Siege ended; determining the new owner.</summary>
+    Settlement,
+}