Grocery List

Build a shared grocery list. When User A adds an item, it must appear instantly on User B's screen. Group items by category (have a common items<=>categories list predefined). Single input at the top (with auto-complete up to 6 items), always visible, type and hit Enter to add. Support optional quantity like 'Milk x2' with a small stepper, and if the item already exists just bump the quantity. Each item has a checkbox, name, quantity, and a small delete button. Tapping an item toggles checked/unchecked — checked items get strikethrough with faded text and sink to the bottom of their category. Add a 'Clear checked' button to bulk-remove completed items. Clean mobile-first design with big tap targets, soft category icons, subtle add/remove animations, and light mode support.