feat: rebuild Tutorial scene avec ProBuilder, matériaux gel/terrain

- Scène Tutorial reconstruite de zéro : sol ProBuilder 120x120, murs, rampes
- Zones race : 5 checkpoints (CP0→Finish) avec BoxCollider + CheckpointTrigger
- Gel pads : GelOrange (boost), GelBleu (bounce), GelViolet (sticky)
- Plateforme centrale pour mode teams (CaptureZone)
- Nouveaux matériaux URP : FloorMat, WallMat, CheckpointMat, GelOrangeMat, GelBleuMat, GelVioletMat, PlatformMat

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

game/.gitattributes

@@ -0,0 +1,60 @@
+# Unity YAML
+*.meta merge=unityyamlmerge eol=lf
+*.unity merge=unityyamlmerge eol=lf
+*.asset merge=unityyamlmerge eol=lf
+*.prefab merge=unityyamlmerge eol=lf
+*.physicMaterial text eol=lf
+*.mat text eol=lf
+*.anim text eol=lf
+*.controller text eol=lf
+*.overrideController text eol=lf
+*.playable text eol=lf
+*.mask text eol=lf
+*.brush text eol=lf
+*.flare text eol=lf
+*.fontsettings text eol=lf
+*.guiskin text eol=lf
+*.giparams text eol=lf
+*.renderTexture text eol=lf
+*.spriteatlas text eol=lf
+*.terrainlayer text eol=lf
+*.mixer text eol=lf
+*.shadergraph text eol=lf
+*.shadersubgraph text eol=lf
+*.inputactions text eol=lf
+
+# Image
+*.jpg filter=lfs diff=lfs merge=lfs -text
+*.jpeg filter=lfs diff=lfs merge=lfs -text
+*.png filter=lfs diff=lfs merge=lfs -text
+*.gif filter=lfs diff=lfs merge=lfs -text
+*.psd filter=lfs diff=lfs merge=lfs -text
+*.ai filter=lfs diff=lfs merge=lfs -text
+*.tif filter=lfs diff=lfs merge=lfs -text
+*.tga filter=lfs diff=lfs merge=lfs -text
+*.exr filter=lfs diff=lfs merge=lfs -text
+*.hdr filter=lfs diff=lfs merge=lfs -text
+
+# Audio
+*.mp3 filter=lfs diff=lfs merge=lfs -text
+*.wav filter=lfs diff=lfs merge=lfs -text
+*.ogg filter=lfs diff=lfs merge=lfs -text
+
+# Video
+*.mp4 filter=lfs diff=lfs merge=lfs -text
+*.mov filter=lfs diff=lfs merge=lfs -text
+
+# 3D Object
+*.fbx filter=lfs diff=lfs merge=lfs -text
+*.obj filter=lfs diff=lfs merge=lfs -text
+*.blend filter=lfs diff=lfs merge=lfs -text
+
+# Fonts
+*.ttf filter=lfs diff=lfs merge=lfs -text
+*.otf filter=lfs diff=lfs merge=lfs -text
+
+# Other
+*.dll filter=lfs diff=lfs merge=lfs -text
+*.a filter=lfs diff=lfs merge=lfs -text
+*.so filter=lfs diff=lfs merge=lfs -text
+*.reason text eol=lf