feat(maps): add Acheron, Debenter, Uruk, Ferea (maps 83-86)

Same pattern as Arkania: terrain resources Terrain84-87.att, map
initializer classes, registration, and update-plugin (v97) that
creates each map + spawn gate + /move warp AND assigns it to the
game server configuration so it is hosted. Also fix the Arkania
update-plugin to assign the game server config (was missing).

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

src/Persistence/Initialization/Updates/UpdateVersion.cs

@@ -489,4 +489,9 @@ public enum UpdateVersion
     /// The version of the <see cref="AddArkaniaMapUpdateSeason6"/>.
     /// </summary>
     AddArkaniaMapSeason6 = 96,
+
+    /// <summary>
+    /// The version of the <see cref="AddImportedMapsUpdateSeason6"/> (Acheron, Debenter, Uruk, Ferea).
+    /// </summary>
+    AddImportedMapsSeason6 = 97,
 }