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/stats/+page.server.ts

@@ -15,9 +15,9 @@ export const load: PageServerLoad = async ({ url, locals }) => {
 			requiresAuth: true
 		};
 	}
-	
+
 	const userId = locals.user.id;
-	
+
 	if (!userId) {
 		return {
 			stats: null,
@@ -27,6 +27,10 @@ export const load: PageServerLoad = async ({ url, locals }) => {
 		};
 	}
 
+	// Get user's current date from timezone query param
+	const timezone = url.searchParams.get('tz') || 'UTC';
+	const userToday = new Date().toLocaleDateString('en-CA', { timeZone: timezone });
+
 	try {
 		// Get all completions for this user
 		const completions = await db
@@ -85,26 +89,29 @@ export const load: PageServerLoad = async ({ url, locals }) => {
 		const sortedDates = completions
 			.map((c: DailyCompletion) => c.date)
 			.sort();
-		
+
 		let currentStreak = 0;
 		let bestStreak = 0;
 		let tempStreak = 1;
-		
+
 		if (sortedDates.length > 0) {
 			// Check if current streak is active (includes today or yesterday)
-			const today = new Date().toISOString().split('T')[0];
-			const yesterday = new Date(Date.now() - 24 * 60 * 60 * 1000).toISOString().split('T')[0];
+			// Use the user's local date passed from the client
+			const today = userToday;
+			const yesterdayDate = new Date(userToday);
+			yesterdayDate.setDate(yesterdayDate.getDate() - 1);
+			const yesterday = yesterdayDate.toISOString().split('T')[0];
 			const lastPlayedDate = sortedDates[sortedDates.length - 1];
-			
+
 			if (lastPlayedDate === today || lastPlayedDate === yesterday) {
 				currentStreak = 1;
-				
+
 				// Count backwards from the most recent date
 				for (let i = sortedDates.length - 2; i >= 0; i--) {
 					const currentDate = new Date(sortedDates[i + 1]);
 					const prevDate = new Date(sortedDates[i]);
 					const daysDiff = Math.floor((currentDate.getTime() - prevDate.getTime()) / (1000 * 60 * 60 * 24));
-					
+
 					if (daysDiff === 1) {
 						currentStreak++;
 					} else {
@@ -112,14 +119,14 @@ export const load: PageServerLoad = async ({ url, locals }) => {
 					}
 				}
 			}
-			
+
 			// Calculate best streak
 			bestStreak = 1;
 			for (let i = 1; i < sortedDates.length; i++) {
 				const currentDate = new Date(sortedDates[i]);
 				const prevDate = new Date(sortedDates[i - 1]);
 				const daysDiff = Math.floor((currentDate.getTime() - prevDate.getTime()) / (1000 * 60 * 60 * 24));
-				
+
 				if (daysDiff === 1) {
 					tempStreak++;
 				} else {
@@ -246,4 +253,4 @@ function getGradeFromGuesses(guessCount: number): string {
 	if (guessCount >= 7 && guessCount <= 10) return "B";
 	if (guessCount >= 11 && guessCount <= 15) return "C+";
 	return "C";
-}
+}