SAN FRANCISCO — Gui Santos already has an idea of what the financial security from the $15 million extension he signed Saturday means for him — and his fiancee. “Now I can get some more Guis,” the 23-year-old wing said while grinning after the Warriors ’ lopsided loss to the Lakers. That was the news Santos’ parents thought their son was calling about when he phoned them back in Brazil after putting pen to paper on a new three-year contract with Golden State and told them he had “something