[FRONTEND] UI/UX refinements for navigation and home responsiveness

[edehvictor]

Closes #663
Closes #662
Closes #655
Closes #629

Changes

• Improved mobile navigation accessibility in AppNav with Escape handling and stronger ARIA labels.
• Ensured mobile nav links close the drawer consistently and prevented background scroll while drawer is open.
• Refined Home page responsiveness and semantic structure (main/section landmarks).
• Added/updated tests for mobile drawer behavior and Home page semantics/navigation actions.

Testing

• Not run in this environment (frontend dependency install was interrupted before vitest became available).

[drips-wave]

@edehvictor Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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