Implement client-side timezone handling for daily verses

Refactored the daily verse system to properly handle users across different
timezones. Previously, the server used a fixed timezone (America/New_York),
causing users in other timezones to see incorrect verses near midnight.

Key changes:

**Server-side refactoring:**
- Extract `getVerseForDate()` into `src/lib/server/daily-verse.ts` for reuse
- Page load now uses UTC date for initial SSR (fast initial render)
- New `/api/daily-verse` POST endpoint accepts client-calculated date
- Server no longer calculates dates; uses client-provided date directly

**Client-side timezone handling:**
- Client calculates local date using browser's timezone on mount
- If server date doesn't match local date, fetches correct verse via API
- Changed verse data from `$derived` to `$state` to fix reactivity issues
- Mutating props was causing updates to fail; now uses local state
- Added effect to reload page when user returns to stale tab on new day

**Stats page improvements:**
- Accept `tz` query parameter for accurate streak calculations
- Use client's local date when determining "today" for current streaks
- Prevents timezone-based streak miscalculations

**Developer experience:**
- Added debug panel showing client local time vs daily verse date
- Added console logging for timezone fetch process
- Comprehensive test suite for timezone handling and streak logic

**UI improvements:**
- Share text uses 📜 emoji for logged-in users, 📖 for anonymous
- Stats link now includes timezone parameter for accurate display

This ensures users worldwide see the correct daily verse for their local
date, and streaks are calculated based on their timezone, not server time.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/routes/+page.svelte

@@ -25,8 +25,9 @@
 
 	let { data }: PageProps = $props();
 
-	let dailyVerse = $derived(data.dailyVerse);
-	let correctBookId = $derived(data.correctBookId);
+	let dailyVerse = $state(data.dailyVerse);
+	let correctBookId = $state(data.correctBookId);
+	let correctBook = $state(data.correctBook);
 	let user = $derived(data.user);
 	let session = $derived(data.session);
 
@@ -178,6 +179,56 @@
 		return id;
 	}
 
+	// If server date doesn't match client's local date, fetch timezone-correct verse
+	$effect(() => {
+		if (!browser) return;
+
+		const localDate = new Date().toLocaleDateString('en-CA');
+		console.log('Date check:', { localDate, verseDate: dailyVerse.date, match: dailyVerse.date === localDate });
+
+		if (dailyVerse.date === localDate) return;
+
+		const timezone = Intl.DateTimeFormat().resolvedOptions().timeZone;
+		console.log('Fetching timezone-correct verse:', { localDate, timezone });
+
+		fetch('/api/daily-verse', {
+			method: 'POST',
+			headers: {
+				'Content-Type': 'application/json',
+			},
+			body: JSON.stringify({
+				date: localDate,
+				timezone,
+			}),
+		})
+			.then((res) => res.json())
+			.then((result) => {
+				console.log('Received verse data:', result);
+				dailyVerse = result.dailyVerse;
+				correctBookId = result.correctBookId;
+				correctBook = result.correctBook;
+			})
+			.catch((err) => console.error('Failed to fetch timezone-correct verse:', err));
+	});
+
+	// Reload when the user returns to a stale tab on a new calendar day
+	$effect(() => {
+		if (!browser) return;
+
+		const loadedDate = new Date().toLocaleDateString('en-CA');
+
+		function onVisibilityChange() {
+			if (document.hidden) return;
+			const now = new Date().toLocaleDateString('en-CA');
+			if (now !== loadedDate) {
+				window.location.reload();
+			}
+		}
+
+		document.addEventListener('visibilitychange', onVisibilityChange);
+		return () => document.removeEventListener('visibilitychange', onVisibilityChange);
+	});
+
 	// Initialize anonymous ID
 	$effect(() => {
 		if (!browser) return;
@@ -388,12 +439,26 @@
 			new Date(`${dailyVerse.date}T00:00:00`),
 		);
 		const siteUrl = window.location.origin;
-		return [
-			`📖 Bibdle | ${formattedDate} 📖`,
+
+		// Use scroll emoji for logged-in users, book emoji for anonymous
+		const bookEmoji = user ? "📜" : "📖";
+
+		const lines = [
+			`${bookEmoji} Bibdle | ${formattedDate} ${bookEmoji}`,
 			`${grade} (${guesses.length} ${guesses.length === 1 ? "guess" : "guesses"})`,
+		];
+
+		// Add streak for logged-in users (requires streak field in user data)
+		if (user && (user as any).streak !== undefined) {
+			lines.push(`🔥 ${(user as any).streak} day streak`);
+		}
+
+		lines.push(
 			`${emojis}${guesses.length === 1 && chapterCorrect ? " ⭐" : ""}`,
-			siteUrl,
-		].join("\n");
+			siteUrl
+		);
+
+		return lines.join("\n");
 	}
 
 	async function share() {
@@ -527,7 +592,7 @@
 		<div class="mt-8 flex flex-col items-stretch md:items-center gap-3">
 			<div class="flex flex-col md:flex-row gap-3">
 				<a
-					href="/stats?{user ? `userId=${user.id}` : `anonymousId=${anonymousId}`}"
+					href="/stats?{user ? `userId=${user.id}` : `anonymousId=${anonymousId}`}&tz={encodeURIComponent(Intl.DateTimeFormat().resolvedOptions().timeZone)}"
 					class="inline-flex items-center justify-center px-4 py-2 bg-amber-600 text-white rounded-lg hover:bg-amber-700 transition-colors text-sm font-medium shadow-md"
 				>
 					📊 View Stats
@@ -558,6 +623,9 @@
 					<div>User: {user ? `${user.email} (ID: ${user.id})` : 'Not signed in'}</div>
 					<div>Session: {session ? `Expires ${session.expiresAt.toLocaleDateString()}` : 'No session'}</div>
 					<div>Anonymous ID: {anonymousId || 'Not set'}</div>
+					<div>Client Local Time: {new Date().toLocaleString('en-US', { timeZone: Intl.DateTimeFormat().resolvedOptions().timeZone, timeZoneName: 'short' })}</div>
+					<div>Client Local Date: {new Date().toLocaleDateString('en-CA')}</div>
+					<div>Daily Verse Date: {dailyVerse.date}</div>
 				</div>
 				<DevButtons />
 			{/if}