Redesign stats page with dark theme and enhanced statistics

- Implement dark gradient background with glassmorphism cards
- Add new statistics: worst day, best book, most seen book, unique books by testament
- Design mobile-first responsive grid layout with optimized spacing
- Update Container component to support dark theme (bg-white/10, border-white/20)
- Calculate book-specific stats by linking completions to daily verses
- Improve visual hierarchy with icons and color-coded stat cards

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

src/lib/utils/stats.ts

@@ -18,6 +18,21 @@ export interface UserStats {
 		guessCount: number;
 		grade: string;
 	}>;
+	worstDay: {
+		date: string;
+		guessCount: number;
+	} | null;
+	bestBook: {
+		bookId: string;
+		avgGuesses: number;
+		count: number;
+	} | null;
+	mostSeenBook: {
+		bookId: string;
+		count: number;
+	} | null;
+	totalBooksSeenOT: number;
+	totalBooksSeenNT: number;
 }
 
 export function getGradeColor(grade: string): string {