Add main menu scene with Rive UI, procedural background, and scene transitions

- Add Menu scene with Rive-driven login and navigation UI
  (RiveLoginController, RiveNavigationController) for entering a
  username and starting/navigating the client via Rive triggers
- Add SceneTransitionController to fade out and load the Landscape
  gameplay scene when Play is selected
- Add procedural low-poly triangle field background and animated wave
  panel (LowPolyTriangleField, TriangleWavePanel) with matching
  editor menus and materials
- Add MenuLightAnimator for animated menu lighting and UI fade helpers
  (MenuFadeIn, DebugFadeToggle/Bridge)
- Rename SampleScene to Landscape and wire ChatNetworkManager to hide
  the new Rive login canvas once gameplay starts
- Bump Input System action codegen version and add Rive package
  references/project settings updates to support the new UI

ProjectSettings/EditorSettings.asset

@@ -3,7 +3,7 @@
 --- !u!159 &1
 EditorSettings:
   m_ObjectHideFlags: 0
-  serializedVersion: 15
+  serializedVersion: 16
   m_SerializationMode: 2
   m_LineEndingsForNewScripts: 0
   m_DefaultBehaviorMode: 0
@@ -23,6 +23,8 @@ EditorSettings:
   m_EnableTextureStreamingInPlayMode: 1
   m_EnableEditorAsyncCPUTextureLoading: 0
   m_AsyncShaderCompilation: 1
+  m_BlockShaders: 0
+  m_UnlockBlockShaders: 0
   m_PrefabModeAllowAutoSave: 1
   m_EnterPlayModeOptionsEnabled: 1
   m_EnterPlayModeOptions: 0
@@ -41,10 +43,11 @@ EditorSettings:
   m_CacheServerNamespacePrefix: default
   m_CacheServerEnableDownload: 1
   m_CacheServerEnableUpload: 1
-  m_CacheServerEnableAuth: 0
   m_CacheServerEnableTls: 0
+  m_CacheServerImportResultCachingEnabled: 0
   m_CacheServerValidationMode: 2
   m_CacheServerDownloadBatchSize: 128
   m_EnableEnlightenBakedGI: 0
   m_ReferencedClipsExactNaming: 1
   m_ForceAssetUnloadAndGCOnSceneLoad: 1
+  m_HideBuildProfileClassicPlatforms: 0