fix: Update to Tailwind v4 CSS theme configuration

- Replace v3 tailwind.config.js with v4 @theme directive
- Move custom colors and animations to CSS @theme block
- CSS now properly includes custom colors (dark-bg, primary, etc.)
- Increases bundle size from 5KB to 29KB (proper styling included)

src/index.css

@@ -1,3 +1,25 @@
-@tailwind base;
-@tailwind components;
-@tailwind utilities;
+@import "tailwindcss";
+
+@theme {
+  --font-sans: 'Inter', sans-serif;
+
+  --color-primary: #00ff9b;
+  --color-primary-dark: #00cc7c;
+  --color-secondary: #2d6ae3;
+  --color-dark-bg: #0a0a0f;
+  --color-dark-card: #121218;
+  --color-dark-border: rgba(255, 255, 255, 0.1);
+
+  --animate-fade-in-up: fadeInUp 0.8s ease-out forwards;
+  --animate-subtle-shine: subtleShine 5s infinite ease-in-out;
+}
+
+@keyframes fadeInUp {
+  0% { opacity: 0; transform: translateY(20px); }
+  100% { opacity: 1; transform: translateY(0); }
+}
+
+@keyframes subtleShine {
+  0%, 100% { box-shadow: 0 0 10px -5px rgba(0, 255, 155, 0); }
+  50% { box-shadow: 0 0 40px -10px rgba(0, 255, 155, 0.3); }
+}