Global Hot Tub Market Size, Share & Demand Report By Product Type (Portable Hot Tubs, In-ground Hot Tubs, Inflatable Hot Tubs), By Material (Acrylic, Fiberglass, Rotomolded Plastic, Wooden), By Capacity (Small (2–3 Persons), Medium (4–6 Persons), Large (7+ Persons)), By Application (Residential, Commercial (Hospitality, Wellness Centers & Spas, Fitness Centers)), By Distribution Channel (Offline Retail, Online Retail), By Technology (Conventional Hot Tubs, Smart Hot Tubs) By Region & Segment Forecasts, 2026–2031