PARIS — Last day of the show season, and Miuccia Prada’s Miu Miu gave a fabulous sendoff to Spring ‘24. She said she usually has a theory about fashion — the collection was called “A Rationale of Beauties” — but this time she worked without a theoretical safety net and showed “what I really, personally like.” The reference in her show manifesto to “the joy of life” came straight to the point of clothes that were, in…