In a movie year rife with grand, three-hour opuses from auteur filmmakers comes a slender 81-minute gem that outclasses them all. Aki Kaurismäki’s “Fallen Leaves,” short, sweet and utterly delightful, is the kind of movie that’s so charming, you want to run it back the moment it’s over. Kaurismäki, the writer-director Finnish master of the deadpan,…