How do the rulings of the hadith: "Whoever prays to Allah twelve rak'ahs in a day and a night, a house will be built for him in Paradise" apply to Friday, taking into consideration that there is no pre-Jumu'ah sunnah prayer?

There is no [prescribed] Sunnah prayer before Jumu'ah. Rather, it has a regular post-prayer Sunnah. The day of Jumu'ah is an exception to the general [meaning] of the Hadith: "There is no Muslim servant who prays to Allah twelve voluntary rak'ahs every day, besides the obligatory prayers, but Allah will build for him a house in Paradise." Its post-prayer regular Sunnah is four rak'ahs absolutely, whether traveling or resident, and whether he prays them in the mosque or at home.