Mayor Zohran Mamdani posts a video on X celebrating Tax Day. @NYCMayor /X A friend of mine who runs a big finance-related firm here in New York City is scouting for new digs in Miami — not only for office space but also a house — and it’s not just about the taxes.  This fella, who spoke on the condition of anonymity, is a name-brand financial type. He’ll make headlines if he decides to bolt. He employs plenty of people — from highly compensated executives to middle-class support staff. They all pay their taxes in addition to their mortgages and grocery bills. They drop plenty of cash at the Big Apple’s restaurants and theaters. The higher-ups are big donors to local charities, the museums and the opera.  He says he hasn’t made up his mind just yet but based on the tenor of our conversation, he has at least one foot out the proverbial door.…