feat(castle-siege): adopt the upstream Castle Siege data model and persistence

Brings in the database layer of upstream OpenMU PRs #754 and #860 without
touching AdaMu's working Castle Siege gameplay. This is purely additive: the
existing 5-phase implementation still runs exactly as before.

What is included:

- DataModel: CastleSiegeState (the original Season 6 values 0-9, which are
  exactly what the game client's CASTLESIEGE_STATE enum expects),
  CastleSiegeJoinSide, and the zone/NPC/upgrade definition types.
- Entities: CastleSiegeData, CastleSiegeGuildRegistration, CastleSiegeNpcState.
  These identify a guild by its persistent Guid rather than by name.
- Generated persistence: 8 BasicModel + 8 EntityFramework model classes,
  CastleSiegeExtensions, and the regenerated ExtendedTypeContext,
  MapsterConfigurator and GameConfiguration partials.
- Migrations: 20260730194321_AddCastleSiege and
  20260801162427_ConfigureCastleSiegePersistence, plus the model snapshot.
- EntityDataContext gains the two DbSets and the five model registrations.
- EntityFrameworkContextBase only publishes configuration changes for entities
  in the configuration schema, so siege state writes are no longer broadcast as
  configuration changes.

AdaMu-specific adaptations:

- UpdateVersion.AddCastleSiegeData is 105, not upstream's 100. AdaMu already
  ships 95-104, and the applied-update bookkeeping is keyed on this value, so a
  collision would skip or re-run updates on live databases.
- CastleSiegeInitializer does not seed a weekly StateSchedule. Upstream drives
  the cycle from a fixed Saturday schedule; AdaMu drives it manually from
  CastleSiegeEventPlugIn and the AdminPanel, so the schedule is left empty and
  nothing reads it.

The seeded NPC definitions match AdaMu's existing hard-coded coordinates
exactly (6 gates, the two crown switches and the crown), and additionally
provide 4 guardian statues, 6 guardsmen and real gate/statue hit point tables
that the current implementation does not have yet.

Two pre-existing migrations were restyled by upstream (copyright header, using
placement, trailing comma). No functional change.

Verified: full server build succeeds with 0 errors.

src/Persistence/EntityFramework/Extensions/ModelBuilder/CastleSiegeExtensions.cs

@@ -0,0 +1,85 @@
+// <copyright file="CastleSiegeExtensions.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.Persistence.EntityFramework.Extensions.ModelBuilder;
+
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using MUnique.OpenMU.Persistence.EntityFramework.Model;
+
+/// <summary>
+/// Extensions for Castle Siege-related <see cref="EntityTypeBuilder"/>s.
+/// </summary>
+internal static class CastleSiegeExtensions
+{
+    /// <summary>
+    /// Applies the settings for the <see cref="CastleSiegeConfiguration"/> entity.
+    /// </summary>
+    /// <param name="builder">The builder.</param>
+    public static void Apply(this EntityTypeBuilder<CastleSiegeConfiguration> builder)
+    {
+        builder.Property(configuration => configuration.CrownHoldTimeSeconds).HasDefaultValue(30);
+        builder.Property(configuration => configuration.RegisterMinLevel).HasDefaultValue(200);
+        builder.Property(configuration => configuration.RegisterMinMembers).HasDefaultValue(20);
+        builder.Property(configuration => configuration.MaxAttackingGuilds).HasDefaultValue(3);
+
+        builder.HasOne(configuration => configuration.RawCastleSiegeMapDefinition)
+            .WithMany()
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(configuration => configuration.RawLandOfTrialsMapDefinition)
+            .WithMany()
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasOne(configuration => configuration.RawRewardItemDefinition)
+            .WithMany()
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+
+    /// <summary>
+    /// Applies the settings for the <see cref="CastleSiegeNpcDefinition"/> entity.
+    /// </summary>
+    /// <param name="builder">The builder.</param>
+    public static void Apply(this EntityTypeBuilder<CastleSiegeNpcDefinition> builder)
+    {
+        builder.HasOne(definition => definition.RawMonsterDefinition)
+            .WithMany()
+            .IsRequired()
+            .OnDelete(DeleteBehavior.Restrict);
+        builder.HasIndex(definition => new { definition.MonsterDefinitionId, definition.InstanceId });
+    }
+
+    /// <summary>
+    /// Applies the settings for the <see cref="CastleSiegeData"/> entity.
+    /// </summary>
+    /// <param name="builder">The builder.</param>
+    public static void Apply(this EntityTypeBuilder<CastleSiegeData> builder)
+    {
+        builder.HasOne<Guild>()
+            .WithMany()
+            .HasForeignKey(data => data.OwnerGuildId)
+            .OnDelete(DeleteBehavior.SetNull);
+    }
+
+    /// <summary>
+    /// Applies the settings for the <see cref="CastleSiegeNpcState"/> entity.
+    /// </summary>
+    /// <param name="builder">The builder.</param>
+    public static void Apply(this EntityTypeBuilder<CastleSiegeNpcState> builder)
+    {
+        builder.HasIndex(state => new { state.MonsterNumber, state.InstanceId }).IsUnique();
+    }
+
+    /// <summary>
+    /// Applies the settings for the <see cref="CastleSiegeGuildRegistration"/> entity.
+    /// </summary>
+    /// <param name="builder">The builder.</param>
+    public static void Apply(this EntityTypeBuilder<CastleSiegeGuildRegistration> builder)
+    {
+        builder.Property(registration => registration.GuildName).HasMaxLength(8).IsRequired();
+        builder.HasIndex(registration => registration.GuildId).IsUnique();
+        builder.HasOne<Guild>()
+            .WithMany()
+            .HasForeignKey(registration => registration.GuildId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}