Implement task list view (GET /tasks)

Add task list page:

• GET /tasks route returning Lucid HTML
• Show all tasks in a table: ID (linked), title, status badge, priority
• Status shown as colored badge (Open=yellow, InProgress=blue, Review=purple, Done=green)
• Mobile-friendly: single column layout, large touch targets
• Use TaskCore.loadTasks to get task data
• Link each task ID to /tasks/:id