[Frontend] Implement comprehensive keyboard navigation and shortcuts system

[Penielka]

Description

Build on existing ARIA improvements by adding a keyboard shortcuts system. All interactive elements should be reachable via Tab, major actions should have shortcut keys (e.g., Ctrl+K for search, Esc to close modals), and a keyboard shortcut help dialog should be available (? key).

Definition of Done

• All interactive elements have visible focus indicators
• Tab order follows logical reading order
• Skip-to-content link on all pages
• Global shortcuts: Ctrl+K (search), ? (shortcuts help), Esc (close/dismiss)
• Page-specific shortcuts for common actions
• Keyboard shortcuts dialog listing all available shortcuts
• Shortcuts do not conflict with browser/OS defaults
• Focus trap implemented in modals, drawers, and dropdowns

Acceptance Criteria

1. Press Tab to navigate through all interactive elements in order
2. Press ? to see keyboard shortcuts dialog
3. Press Esc to close any modal/dialog
4. Focus ring is visible on all focused elements
5. Skip-to-content link appears on first Tab press

Files to Modify

• New file: frontend/src/hooks/useKeyboardShortcuts.ts — global shortcut handler
• New file: frontend/src/components/KeyboardShortcutsDialog.tsx — help dialog
• frontend/src/hooks/useFocusTrap.ts — enhance focus trap behavior
• frontend/src/app/layout.tsx — add skip-to-content link
• Multiple component files — add tabIndex, aria attributes, role attributes
• frontend/src/styles/globals.css — ensure visible focus ring styles

[gloskull]

Hello, I have 4 years of experience delivering solutions for projects like this, covering backend, frontend, and smart contract development. After carefully reviewing your requirements, I have a clear understanding of the task and am confident in my ability to deliver a clean, efficient, and thoroughly tested solution on time. I prioritize code quality, maintainability, and industry best practices throughout the development process.
My PR will be submitted in under 10hours.

[clintjeff2]

Hello, I have 6 years of experience working on tasks like this and handling similar challenges across backend, frontend, and smart-contract development. I have carefully read and fully understood the task requirements, and I am confident I can deliver a clean, efficient, and well-tested solution promptly. I always ensure high-quality implementation, maintainability, and adherence to best practices.

Pull request in 5 hours.