Create a realistic mockup of a long, vertical coffee bag. The packaging should be completely white, minimalistic, and elegant, with no design, no graphics, and no seal lines or wrinkles at the top. The surface must look clean, smooth, and premium. Place the bag on a stylish, modern background with a soft, elegant color palette (no busy textures). Add subtle shadows for a natural and professional look. No logos, no text, no patterns — just a blank premium coffee bag.