style: adjust gradient fade radius in StackSection

- Reduced gradient fade-out radius from 90% to 30% for more concentrated visual effect
- Adjusted middle gradient stop from 50% to 20% to create smoother transition
- Fine-tuned visual appearance of the radial background gradient in light theme

src/pages/home/StackSection.tsx

@@ -34,7 +34,7 @@ export function StackSectionLight() {
           className="absolute left-[70%] top-[30%] -translate-x-1/2 -translate-y-1/2 w-[1600px] h-[1600px] rounded-full pointer-events-none"
           style={{
             background:
-              "radial-gradient(circle, rgba(100,220,255,0.25) 0%, rgba(200,255,255,0.15) 50%, rgba(255,255,255,0) 90%)",
+              "radial-gradient(circle, rgba(100,220,255,0.25) 0%, rgba(200,255,255,0.15) 20§§%, rgba(255,255,255,0) 30%)",
             filter: "blur(200px)",
           }}
           animate={{