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>

package.json

@@ -11,14 +11,14 @@
   "dependencies": {
     "@hello-pangea/dnd": "^18.0.1",
     "@tailwindcss/vite": "^4.1.11",
-    "react": "^19.1.0",
-    "react-dom": "^19.1.0"
+    "preact": "^10.26.4"
   },
   "devDependencies": {
+    "@preact/preset-vite": "^2.10.1",
     "@tailwindcss/postcss": "^4.1.11",
     "@types/node": "^22.14.0",
     "@types/react": "^19.1.8",
-    "@vitejs/plugin-react": "^4.7.0",
+    "@types/react-dom": "^19.1.5",
     "autoprefixer": "^10.4.21",
     "postcss": "^8.5.6",
     "tailwindcss": "^4.1.11",