living plane: load the module at PostConfigInit (L173)

Its global shader type must register before shader types initialise; at Default loading phase UE asserts on startup.
Found by the Linux UE owner-world smoke of wip/combined; with this change the smoke passes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

VoxelForge.uplugin

@@ -34,7 +34,7 @@
 		{
 			"Name": "VoxelForgeLivingPlane",
 			"Type": "Runtime",
-			"LoadingPhase": "Default"
+			"LoadingPhase": "PostConfigInit"
 		},
 		{
 			"Name": "VoxelForgeEditor",