Add emoji confetti bursts and component playground.

Support app.relay.emoji_confetti on jumbo emoji clicks with canvas physics,
per-emoji particle profiles, and a fixed overlay that does not affect scroll.
Also add a Vite playground for live component previews and theme hover preview.

.gitignore

@@ -4,4 +4,5 @@ node_modules
 devAssets
 
 .DS_Store
-.idea
+.idea
+.cache