feat: confirm dialog for changing decks

src/routes/+page.svelte

@@ -280,6 +280,12 @@
 	}
 
 	function handleDeckChange() {
+		if (!confirm('Are you sure you want to change the deck? This will reset the current session.')) {
+			// If the user cancels, revert the selection
+			const previousDeck = cards.length > 0 ? deckConfigs.findIndex(d => d.cards[0] === cards[0].frontImage) : 0;
+			selectedDeck = previousDeck;
+			return;
+		}
 		initializeDeck();
 	}