There’s a red-sauce-fueled resurgence happening in Little Italy. For decades, the neighborhood seemed to be shrinking.  Once a sprawling 30-block enclave of Italian immigrants, the neighborhood has shrunk to five blocks along Mulberry Street between Canal and Broome. Astronomical rents pushed out multigenerational businesses that had been fixtures for a century. Italian families moved elsewhere. Some old-timers even sounded the death knell. But now, as Little Italy celebrates the 100th anniversary of its famed Feast…