Migrate shaders to URP and add loading screen

Reworks multiple shaders and materials for URP compatibility and adds a Loading screen/scene and a few model imports. Key changes:
- Converted ProBuilder standard vertex-color shader and several particle/surface shaders to URP HLSL passes (UniversalForward, ShadowCaster, Depth, DepthNormals) preserving base texture * tint * vertex color, normal map and PBR parameters.
- Updated particle SurfaceShader_VC to a URP forward pass and simplified lighting to use URP shader library helpers.
- Updated materials (landMark, tile) to point to project textures, adjust keywords/flags (e.g. XRMotionVectorsPass, disable ShadowCaster for one), tweak tiling and base color values.
- Added a Loading screen UI (UXML, USS) and LoadingScreenController.cs plus a new Loading scene and scene metadata.
- Imported new FBX assets (T-Pose, Untitled) and updated Editor build settings / project settings to include the new Loading scene.
These changes migrate rendering code to the Universal Render Pipeline and add a basic loading UI/scene, while updating materials and project settings accordingly.

Assets/Game Kit Controller/Shaders/textShader.shader

@@ -1,17 +1,58 @@
-Shader "Custom/textShader" {
+Shader "Custom/URP_textShader"
+{
 	Properties {
-  	_MainTex ("Font Texture", 2D) = "white" {}
-  	_Color ("Text Color", Color) = (1,1,1,1)
-}
-SubShader {
-	Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
-	  	Lighting Off Cull Off ZWrite Off Fog { Mode Off }
-	  	Blend SrcAlpha OneMinusSrcAlpha
-	  	Pass{
-	   		Color [_Color]
-	   		SetTexture [_MainTex] {
-	    		combine primary, texture * primary
-	   		}
-	  	}
- 	}
+		_MainTex ("Font Texture", 2D) = "white" {}
+		_Color ("Text Color", Color) = (1,1,1,1)
+	}
+	SubShader {
+		Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
+		LOD 100
+		Cull Off
+		ZWrite Off
+		Blend SrcAlpha OneMinusSrcAlpha
+
+		Pass {
+			Name "FORWARD"
+			HLSLPROGRAM
+			#pragma vertex vert
+			#pragma fragment frag
+			#pragma multi_compile_fog
+			#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
+
+			struct Attributes {
+				float4 positionOS : POSITION;
+				float2 uv         : TEXCOORD0;
+			};
+
+			   struct Varyings {
+				   float4 positionHCS : SV_POSITION;
+				   float2 uv          : TEXCOORD0;
+				   float fogFactor    : TEXCOORD1;
+			   };
+
+			CBUFFER_START(UnityPerMaterial)
+				float4 _Color;
+			CBUFFER_END
+
+			TEXTURE2D(_MainTex); SAMPLER(sampler_MainTex);
+
+			Varyings vert(Attributes IN)
+			{
+				Varyings OUT;
+				OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
+				OUT.uv = IN.uv;
+			OUT.fogFactor = ComputeFogFactor(OUT.positionHCS.z / OUT.positionHCS.w);
+				return OUT;
+			}
+
+			float4 frag(Varyings IN) : SV_Target
+			{
+				float4 tex = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, IN.uv);
+				float4 col = tex * _Color;
+			col.rgb = MixFog(col.rgb, IN.fogFactor);
+				return col;
+			}
+			ENDHLSL
+		}
+	}
 }