Fix GradientBlinds scroll drift on mobile and address dampening regression

- Added isMobile detection (<= 768px) in GradientBlinds.tsx
- Updated onPointerMove to calculate container-relative coordinates immediately on mobile
- Updated animation loop to skip scroll-based target updates on mobile
- Fixed regression where disabling mouse dampening on mobile would freeze the spotlight
- Prevents spotlight from drifting across the background during scroll inertia on mobile devices

Co-authored-by: ragusa-it <196988693+ragusa-it@users.noreply.github.com>

src/components/effects/GradientBlinds.tsx

@@ -376,7 +376,7 @@ void main() {
         cur[0] += (target[0] - cur[0]) * factor;
         cur[1] += (target[1] - cur[1]) * factor;
       } else {
-        if (pointerPosRef.current) {
+        if (pointerPosRef.current || isMobileRef.current) {
           uniforms.iMouse.value = mouseTargetRef.current;
         }
         lastTimeRef.current = t;