Kanban view enhancements: filters, column controls, card metadata

Improve the Kanban view with: filter by status (toggle columns on/off); rearrange and set default column order; filter by date across List/Kanban/Queue views; hide/show specific columns (e.g. 'Closed'); show count of tasks per stage on column headers; show task priority on cards; show how long a task has been in its current stage; and creating requests directly from the Kanban view.