Add design spec for OpenGL 3D view

Replaces the JavaFX SubScene/MeshView rendering with an OpenGL viewport
(openglfx-jogl, GL 3.3 core), single global VBO, GPU color-picking, and
baked fake shading. Windows/Linux targets; JavaFX 3D path removed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/datastructure/FeatureType.java

@@ -27,5 +27,5 @@ public enum FeatureType {
 
     BUILDING, TRANSPORTATION, VEGETATION, BRIDGE, LAND, WATER, BOUNDARY_SURFACE, INSTALLATION, OPENING,
     BUILDING_PART, BUILDING_SUBDIVISION, BRIDGE_CONSTRUCTION_ELEMENT, BRIDGE_INSTALLATION, ROOM, FURNITURE, CITY_FURNITURE,
-    GENERIC_CITY_OBJECT, TUNNEL, TUNNEL_PART, TUNNEL_CONSTRUCTION_ELEMENT, TUNNEL_INSTALLATION,
+    OTHER_CITY_OBJECT, TUNNEL, TUNNEL_PART, TUNNEL_CONSTRUCTION_ELEMENT, TUNNEL_INSTALLATION,
 }