Global Leafy Vegetable Market Size, Share Demand Report By Product Type (Lettuce, Spinach, Cabbage, Kale & Specialty Greens), By Category (Conventional, Organic), By Farming Method (Open-Field, Greenhouse, Hydroponics/Vertical Farming), By Distribution Channel (Supermarkets & Hypermarkets, Online Retail, Specialty Stores / Farmers’ Markets), By End Use (Household Consumption, Foodservice, Ready-to-Eat, Exports & Institutional Supply) By Region & Segment Forecasts, 2026–2031