Make gradient background unaffected by scene lighting

Set background layer's alpha blending mode to disable and texture's hasAlpha to false.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 2ada40c2-c083-4794-9179-1abaa00b4437
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: 8bf651fe-9f0a-4062-add6-3b56da178c7c
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1099a351-df60-40b5-bf61-4999bad0d153/2ada40c2-c083-4794-9179-1abaa00b4437/HcCrJhS

Author: TracyGardner

api/scene.js

@@ -66,6 +66,10 @@ export const flockScene = {
         const layer = new flock.BABYLON.Layer("backgroundGradientLayer", null, flock.scene, true);
         layer.texture = dt;
         layer.isBackground = true;
+        
+        // Ensure the layer is completely unlit and unaffected by scene lighting
+        layer.alphaBlendingMode = flock.BABYLON.Constants.ALPHA_DISABLE;
+        dt.hasAlpha = false;
         dt.wrapU = flock.BABYLON.Texture.CLAMP_ADDRESSMODE;
         dt.wrapV = flock.BABYLON.Texture.CLAMP_ADDRESSMODE;