feat(CS): castle flag owner logo (C1 B9 02) + catapults for war atmosphere

#1 Castle flags now show the owner guild's logo: resolve owner name -> guild logo
(cached), broadcast C1 B9 02 (32-byte mark) to players on the castle map every 15s.
#3 War atmosphere: spawn catapult NPCs 221/222 at siege start (client renders them
as siege weapons); the 0xB2/0x17 start flag already flips the map to warzone mode.
All raw S6 packets, no client changes.

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

src/GameLogic/Views/CastleSiege/ICastleSiegeStatusViewPlugIn.cs

@@ -22,4 +22,10 @@ public interface ICastleSiegeStatusViewPlugIn : IViewPlugIn
     /// <param name="hour">The remaining hours.</param>
     /// <param name="minute">The remaining minutes.</param>
     ValueTask SetTimerAsync(byte hour, byte minute);
+
+    /// <summary>
+    /// Sends the castle owner guild's 32-byte logo (C1 B9 02) so the client paints it onto the castle flags.
+    /// </summary>
+    /// <param name="guildLogo">The owner guild's 32-byte logo/emblem.</param>
+    ValueTask SetCastleFlagAsync(ReadOnlyMemory<byte> guildLogo);
 }