Alden & Harlow, the restaurant that opened Friday in its location under Cafe Algiers on 40 Brattle St., pays homage to Harvard Square with its decor, its independent ownership, and even its personnel. Featuring many of the murals that decorated the walls of its predecessor, the new bistro employs a line cook whose great uncle was the original owner of Club Casablanca, the iconic bar that occupied the space for more than 50 years. “The name of the restaurant itself is the ultimate nod to the Square,” owner and chef Michael Scelfo said.