[app-bug] Findings list has no keyboard navigation (j/k, /, ?, esc)

[Gbangbolaoluwagbemiga]

Problem

Auditors who use the dashboard heavily can't navigate findings without a mouse. There is no j/k, no / to focus search, no esc to clear filters, no ? cheat sheet.

Acceptance Criteria

• j / k move the selected finding up/down
• enter opens the selected finding's detail panel
• / focuses the code-filter input
• esc clears focused input and resets selection
• ? opens a modal cheat sheet
• Disabled when an <input> or <textarea> has focus
• Storybook story exercises the shortcuts

Pointers

• frontend/app/components/FindingsList.tsx
• frontend/app/dashboard/page.tsx

Difficulty

Easy. Single hook + ARIA live region.