The founders of the Princess Project want every girl to feel beautiful, if only for one night.On March 17, nearly 3,000 Bay Area high-school girls will enter the old SF Examiner building on Market Street, skeptical, no doubt, that its worse-for-wear exterior could possibly reveal, of all things, prom dresses free for the taking. But if past Princess Project giveaways are any indication, the place will be filled with taffeta in more colors than a Pantone swatch book, and enough tulle for it to be mistaken for the costume closet at the San Francisco Ballet. This year, there’ll even be a DJ.