migrate to Preact and add iOS-feel animations

- Replace React 19 with Preact via @preact/preset-vite (zero component changes needed — Vite aliases react → preact/compat at build time)
- Add custom iOS easing curves (ease-ios, ease-spring) via Tailwind @theme
- Update all transitions to use iOS-standard 200ms durations and spring/decel easing
- Add active:scale press feedback on tiles, buttons, and toggles
- Toggle knob now uses spring easing for a satisfying snap

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/ToggleSwitch.tsx

@@ -11,12 +11,12 @@ const ToggleSwitch: React.FC<ToggleSwitchProps> = ({ checked, onChange }) => {
   };
 
   return (
-    <div 
-      className={`w-14 h-8 flex items-center rounded-full p-1 cursor-pointer transition-colors duration-300 ${checked ? 'bg-cyan-500' : 'bg-gray-600'}`}
+    <div
+      className={`w-14 h-8 flex items-center rounded-full p-1 cursor-pointer transition-colors duration-200 ease-ios ${checked ? 'bg-cyan-500' : 'bg-gray-600'}`}
       onClick={handleToggle}
     >
-      <div 
-        className={`bg-white w-6 h-6 rounded-full shadow-md transform transition-transform duration-300 ${checked ? 'translate-x-6' : 'translate-x-0'}`}
+      <div
+        className={`bg-white w-6 h-6 rounded-full shadow-md transform transition-transform duration-200 ease-spring ${checked ? 'translate-x-6' : 'translate-x-0'}`}
       />
     </div>
   );