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/Mixamo Animations/Crafting/Materials/Alpha_Body_MAT.mat

@@ -132,7 +132,7 @@ Material:
     - _ZWrite: 1
     m_Colors:
     - _BaseColor: {r: 0.09656998, g: 0.42161977, b: 0.522, a: 1}
-    - _Color: {r: 1, g: 1, b: 1, a: 1}
+    - _Color: {r: 0.09656995, g: 0.42161974, b: 0.522, a: 1}
     - _EmissionColor: {r: 0, g: 0, b: 0, a: 1}
     - _SpecColor: {r: 0.19999996, g: 0.19999996, b: 0.19999996, a: 1}
   m_BuildTextureStacks: []

Assets/Mixamo Animations/Crafting/Materials/Alpha_Joints_MAT.mat

@@ -132,7 +132,7 @@ Material:
     - _ZWrite: 1
     m_Colors:
     - _BaseColor: {r: 0.15355149, g: 0.21289384, b: 0.22221711, a: 1}
-    - _Color: {r: 1, g: 1, b: 1, a: 1}
+    - _Color: {r: 0.15355146, g: 0.21289381, b: 0.22221708, a: 1}
     - _EmissionColor: {r: 0, g: 0, b: 0, a: 1}
     - _SpecColor: {r: 0.19999996, g: 0.19999996, b: 0.19999996, a: 1}
   m_BuildTextureStacks: []