feat(items): add Imperial Sword (0/50) and Imperial Staff (5/50)

Two new weapons placed at free item slots so they never collide with
standard Season 6 items. The client name DB (Item_eng.bmd) is the source
of tooltip name/stats, so only free slots are usable for custom items.

Both seed paths are covered:
- Fresh DB: Weapons.Initialize() calls the new CreateImperialWeapons050().
- Existing DB: AddImperialWeapons050UpdateSeason6 (UpdateVersion 95),
  applied from the AdminPanel Updates page, with an idempotency guard.

Imperial Sword is a Magic Gladiator weapon (copy of 0/28), Imperial Staff
is a Wizard weapon (copy of 5/31).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/Persistence/Initialization/Updates/AddImperialWeapons050UpdateSeason6.cs

@@ -0,0 +1,56 @@
+// <copyright file="AddImperialWeapons050UpdateSeason6.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.Persistence.Initialization.Updates;
+
+using System.Runtime.InteropServices;
+using MUnique.OpenMU.DataModel.Configuration;
+using MUnique.OpenMU.Persistence.Initialization.VersionSeasonSix.Items;
+using MUnique.OpenMU.PlugIns;
+
+/// <summary>
+/// Adds two new weapons at item number 50: Imperial Sword (group 0, Magic Gladiator) and
+/// Imperial Staff (group 5, Wizard), as full working weapons (damage, attack speed, requirements,
+/// options, equip flags). Placed at free slots so they never collide with standard items.
+/// </summary>
+[PlugIn]
+[Display(Name = PlugInName, Description = PlugInDescription)]
+[Guid("BE9DD7D1-F352-4C56-A646-D78C36978982")]
+public class AddImperialWeapons050UpdateSeason6 : UpdatePlugInBase
+{
+    internal const string PlugInName = "Add Imperial Weapons (0/50, 5/50)";
+    internal const string PlugInDescription = "Adds Imperial Sword (0/50) and Imperial Staff (5/50) as fully working weapons.";
+
+    /// <inheritdoc />
+    public override UpdateVersion Version => UpdateVersion.AddImperialWeapons050Season6;
+
+    /// <inheritdoc />
+    public override string DataInitializationKey => VersionSeasonSix.DataInitialization.Id;
+
+    /// <inheritdoc />
+    public override string Name => PlugInName;
+
+    /// <inheritdoc />
+    public override string Description => PlugInDescription;
+
+    /// <inheritdoc />
+    public override bool IsMandatory => true;
+
+    /// <inheritdoc />
+    public override DateTime CreatedAt => new(2026, 07, 16, 12, 0, 0, DateTimeKind.Utc);
+
+    /// <inheritdoc />
+#pragma warning disable CS1998
+    protected override async ValueTask ApplyAsync(IContext context, GameConfiguration gameConfiguration)
+#pragma warning restore CS1998
+    {
+        // Idempotency guard: skip if the Imperial Sword 0/50 already exists.
+        if (gameConfiguration.Items.Any(i => i.Group == 0 && i.Number == 50))
+        {
+            return;
+        }
+
+        new Weapons(context, gameConfiguration).CreateImperialWeapons050();
+    }
+}

src/Persistence/Initialization/Updates/UpdateVersion.cs

@@ -479,4 +479,9 @@ public enum UpdateVersion
     /// The version of the <see cref="AddIsQuestItemFlagPlugIn"/>.
     /// </summary>
     AddIsQuestItemFlag = 94,
+
+    /// <summary>
+    /// The version of the <see cref="AddImperialWeapons050UpdateSeason6"/>.
+    /// </summary>
+    AddImperialWeapons050Season6 = 95,
 }