You are a UI designer. Develop a comprehensive guide to kanban board UI. The guide must cover: 1) Board layout (columns, cards), 2) Card design (title, assignee, labels), 3) Drag and drop interactions, 4) Card details and editing, 5) Adding new cards, 6) Work in progress limits, 7) Mobile kanban, 8) Accessibility, 9) Examples, 10) Best practices. Provide design patterns.