feat: nouveau build WebGL last_build + fixes stats et schema Colyseus

- Unity build last_build remplace build_mai
- NetworkSchema.cs: correction types sbyte pour int8 (fix OverflowException Colyseus)
- StatsTracker: envoi periodique toutes les 30s, plus de dependance aux round events
- StatsTracker: cooldown client 6s pour respecter le rate-limit serveur
- StatsPage: correction row.value au lieu de row[activeTab]
- StatsPage: suppression onglet Courses (racesPlayed)
- Backend index.js: logging POST /stats/update
- Scene Tutorial: mise a jour, suppression assets obsoletes (TutorialInfo, physicMaterials)

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

game/Assets/Material/CheckpointMat.mat

@@ -8,8 +8,8 @@ Material:
   m_PrefabInstance: {fileID: 0}
   m_PrefabAsset: {fileID: 0}
   m_Name: CheckpointMat
-  m_Shader: {fileID: 46, guid: 0000000000000000f000000000000000, type: 0}
-  m_Parent: {fileID: 0}
+  m_Shader: {fileID: -6465566751694194690, guid: c52a5eb90c085474582a223ce9475866, type: 3}
+  m_Parent: {fileID: -876546973899608171, guid: c52a5eb90c085474582a223ce9475866, type: 3}
   m_ModifiedSerializedProperties: 0
   m_ValidKeywords: []
   m_InvalidKeywords: []
@@ -22,63 +22,22 @@ Material:
   m_LockedProperties: 
   m_SavedProperties:
     serializedVersion: 3
-    m_TexEnvs:
-    - _BumpMap:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _DetailAlbedoMap:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _DetailMask:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _DetailNormalMap:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _EmissionMap:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _MainTex:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _MetallicGlossMap:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _OcclusionMap:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
-    - _ParallaxMap:
-        m_Texture: {fileID: 0}
-        m_Scale: {x: 1, y: 1}
-        m_Offset: {x: 0, y: 0}
+    m_TexEnvs: []
     m_Ints: []
-    m_Floats:
-    - _BumpScale: 1
-    - _Cutoff: 0.5
-    - _DetailNormalMapScale: 1
-    - _DstBlend: 0
-    - _GlossMapScale: 1
-    - _Glossiness: 0.5
-    - _GlossyReflections: 1
-    - _Metallic: 0
-    - _Mode: 0
-    - _OcclusionStrength: 1
-    - _Parallax: 0.02
-    - _SmoothnessTextureChannel: 0
-    - _SpecularHighlights: 1
-    - _SrcBlend: 1
-    - _UVSec: 0
-    - _ZWrite: 1
-    m_Colors:
-    - _Color: {r: 0.1, g: 0.9, b: 0.3, a: 1}
-    - _EmissionColor: {r: 0, g: 0, b: 0, a: 1}
+    m_Floats: []
+    m_Colors: []
   m_BuildTextureStacks: []
   m_AllowLocking: 1
+--- !u!114 &8924139153543123182
+MonoBehaviour:
+  m_ObjectHideFlags: 11
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 639247ca83abc874e893eb93af2b5e44, type: 3}
+  m_Name: 
+  m_EditorClassIdentifier: Unity.ShaderGraph.Editor::UnityEditor.Rendering.BuiltIn.AssetVersion
+  version: 0