With the finale of the “Harry Potter” movies in theaters now, it’s tempting to try to recapture the fan spirit with Harry Potter: Spells — a free app from Warner Bros. But unless you’re willing to pay for extras, this dueling game can get very tedious, very fast. At the start of the app, users pick a wand and go before the Sorting Hat — don’t worry, you can retry if you end in a house you don’t want. Then, you get to the spells.