Is preparing the bride part of the Sunnah, and are there any proofs for it in Islamic history?

The fundamental principle is that the husband bears the expenses of marriage, the mahr (dowry), furnishing the marital home, and providing for his wife. The woman is not obliged to contribute to any of these unless she does so willingly. This is the reason for the man's guardianship (qawamah) over the woman, as Allah the Almighty says: "Men are maintainers of women, because Allah has made some of them to excel others, and because they spend out of their property." If the woman or her guardian voluntarily contributes some furnishings, or if it is customary, there is no harm in it. The Prophet, peace and blessings be upon him, prepared Fatimah with a velvet cloak, a water skin, and a pillow stuffed with idhkhir (a type of aromatic grass). He also prepared her with a bed and a pillow stuffed with palm fibers, and he instructed Ali to use two-thirds of the mahr for perfumes and one-third for clothing.