At the far end of the spectrum of potential audience for the “Twilight” franchise is the “Twi-Hard” contingent, those fanatic loyalists to the book-turned-movie series who will camp out for a front-row seat, no matter what the reviews say. Their only regret about “The Twilight Saga: Breaking Dawn,” the two-part film whose final installment opens tonight, bringing the five-chapter saga to an end,