Add Rybbit analytics alongside Umami

- Load Rybbit script via app.html (recommended SvelteKit approach)
- Mirror all Umami custom events (First guess, Guessed correctly, Share, Copy to Clipboard, social link clicks) with rybbit.event()
- Identify logged-in users with name/email traits; anonymous users by stable UUID

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

src/lib/components/WinScreen.svelte

@@ -209,7 +209,7 @@
 		<div class="share-buttons">
 			{#if hasWebShare}
 				<button
-					onclick={handleShare}
+					onclick={() => { (window as any).rybbit?.event("Share"); handleShare(); }}
 					data-umami-event="Share"
 					class="share-btn primary"
 				>
@@ -218,6 +218,7 @@
 			{:else}
 				<button
 					onclick={() => {
+						(window as any).rybbit?.event("Copy to Clipboard");
 						copyToClipboard();
 						copySuccess = true;
 						setTimeout(() => {