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/DefaultVolumeProfile.asset

@@ -342,6 +342,9 @@ MonoBehaviour:
   skyOcclusionIntensityMultiplier:
     m_OverrideState: 1
     m_Value: 1
+  worldOffset:
+    m_OverrideState: 1
+    m_Value: {x: 0, y: 0, z: 0}
 --- !u!114 &-1216621516061285780
 MonoBehaviour:
   m_ObjectHideFlags: 3
@@ -376,6 +379,9 @@ MonoBehaviour:
   highQualityFiltering:
     m_OverrideState: 1
     m_Value: 0
+  filter:
+    m_OverrideState: 1
+    m_Value: 0
   downscale:
     m_OverrideState: 1
     m_Value: 0
@@ -462,8 +468,6 @@ MonoBehaviour:
   - {fileID: -6288072647309666549}
   - {fileID: 7518938298396184218}
   - {fileID: -1410297666881709256}
-  - {fileID: -7750755424749557576}
-  - {fileID: -5139089513906902183}
 --- !u!114 &853819529557874667
 MonoBehaviour:
   m_ObjectHideFlags: 3