“Here’s to Champagne problems!” a 20-something brunette in a ball gown cheers, her voice as bubbly as her lifted flute. It’s opening night at Alamo Drafthouse for what bodes to be one of the biggest movies this fall — not a Spielberg thriller, Halloween horror flick or Oscar-baiting period piece, but a film version of the highest-grossing concert tour of all time, starring none other than planet Earth’s favorite blonde American. The megastar’s mane may be more a golden brown these days as she approaches her 34th year, but her iconic bangs and red lips remain.