Content: frame texture maps, scene passes, BlockCam layer prep

- Generated _normal/_height maps for all frame photo textures (DeepBump)
- The Room: picture frame pass; Lobby/Test Map scene passes
- AudioMixer: unmute group
- New layer 8 "BlockCam" (TagManager) + Main Camera culling mask includes it

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scenes/Main.unity

@@ -2011,7 +2011,7 @@ Camera:
   m_Depth: -1
   m_CullingMask:
     serializedVersion: 2
-    m_Bits: 55
+    m_Bits: 311
   m_RenderingPath: -1
   m_TargetTexture: {fileID: 0}
   m_TargetDisplay: 0