feat(ui): bench-experience enhancements — recipe book, export, batch scaling, why-this-carrier

[rvnminers-A-and-N]

Bundle of Formulation Studio quality-of-life features: save/name/reload formulations (recipe book, local-first), export a recipe card/CSV, batch-size scaling (ppm→grams for a target volume), and 'why this carrier' tooltips (notes/GRAS/match/volatility).

Tracks internal tasks #29–#32.