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

Assets/Settings/Mobile_RPAsset.asset

@@ -12,8 +12,8 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: bf2edee5c58d82540a51f03df9d42094, type: 3}
   m_Name: Mobile_RPAsset
   m_EditorClassIdentifier: 
-  k_AssetVersion: 12
-  k_AssetPreviousVersion: 12
+  k_AssetVersion: 13
+  k_AssetPreviousVersion: 13
   m_RendererType: 1
   m_RendererData: {fileID: 0}
   m_RendererDataList:
@@ -53,6 +53,7 @@ MonoBehaviour:
   m_AdditionalLightsShadowResolutionTierHigh: 1024
   m_ReflectionProbeBlending: 1
   m_ReflectionProbeBoxProjection: 1
+  m_ReflectionProbeAtlas: 1
   m_ShadowDistance: 50
   m_ShadowCascadeCount: 1
   m_Cascade2Split: 0.25
@@ -73,16 +74,15 @@ MonoBehaviour:
   m_MixedLightingSupported: 1
   m_SupportsLightCookies: 1
   m_SupportsLightLayers: 1
-  m_DebugLevel: 0
   m_StoreActionsOptimization: 0
   m_UseAdaptivePerformance: 1
   m_ColorGradingMode: 0
   m_ColorGradingLutSize: 32
+  m_AllowPostProcessAlphaOutput: 0
   m_UseFastSRGBLinearConversion: 1
   m_SupportDataDrivenLensFlare: 1
   m_SupportScreenSpaceLensFlare: 1
   m_GPUResidentDrawerMode: 0
-  m_UseLegacyLightmaps: 0
   m_SmallMeshScreenPercentage: 0
   m_GPUResidentDrawerEnableOcclusionCullingInCameras: 0
   m_ShadowType: 1
@@ -109,6 +109,7 @@ MonoBehaviour:
   m_PrefilterDebugKeywords: 1
   m_PrefilterWriteRenderingLayers: 1
   m_PrefilterHDROutput: 1
+  m_PrefilterAlphaOutput: 0
   m_PrefilterSSAODepthNormals: 1
   m_PrefilterSSAOSourceDepthLow: 1
   m_PrefilterSSAOSourceDepthMedium: 0
@@ -126,8 +127,15 @@ MonoBehaviour:
   m_PrefilterSoftShadowsQualityHigh: 1
   m_PrefilterSoftShadows: 0
   m_PrefilterScreenCoord: 1
+  m_PrefilterScreenSpaceIrradiance: 0
   m_PrefilterNativeRenderPass: 1
   m_PrefilterUseLegacyLightmaps: 0
+  m_PrefilterBicubicLightmapSampling: 0
+  m_PrefilterReflectionProbeRotation: 0
+  m_PrefilterReflectionProbeBlending: 0
+  m_PrefilterReflectionProbeBoxProjection: 0
+  m_PrefilterReflectionProbeAtlas: 0
+  m_PrefilterPointSamplingUpsampling: 0
   m_ShaderVariantLogLevel: 0
   m_ShadowCascades: 0
   m_Textures: