Accessibility: Fix keyboard navigation and ARIA attributes across the dashboard UI

[coderabbitai]

Overview

Several accessibility issues were identified during the review of PR #35 (new dashboard UI) that should be addressed holistically in a dedicated PR.

Known Issues

• Sortable table headers in src/app/_stats/stats-table-shell.tsx (lines 55–75): Sort triggers use a clickable <div> instead of a <button>, making them unreachable by keyboard users. Additionally, aria-sort is missing on header cells, so screen readers cannot announce sort direction.
• Additional accessibility issues across the new dashboard components (stat cards, charts, badges, modals) should be audited and addressed as part of this effort.

Suggested Fixes

• Replace clickable <div> elements used as interactive controls with semantic <button> elements.
• Add aria-sort (ascending / descending / none) to sortable <th> cells.
• Audit all new UI components introduced in PR Propose for the new dashboard UI #35 for keyboard focusability, focus management, ARIA roles, and color contrast.

References

• PR: Propose for the new dashboard UI #35
• Review comment: Propose for the new dashboard UI #35 (comment)
• Requested by: @mike1858