fix: add NotFound 404 page and replace silent redirect with proper error page

[pericharlabindhumadhavi-data]

Closes #241

What was the problem?

The application redirected all unknown routes directly to the homepage using a catch-all route.

This behavior provided no indication that the requested page did not exist, making broken links and mistyped URLs difficult for users to understand.

How was it solved?

• Created a dedicated NotFound page.
• Added a user-friendly 404 message.
• Included navigation back to the homepage.
• Replaced the catch-all homepage redirect with the NotFound component.

Impact

• Provides clear feedback when users visit invalid URLs.
• Improves navigation experience.
• Aligns routing behavior with standard web application practices.

Checklist

• Created NotFound page.
• Updated catch-all routing logic.
• Tested invalid route handling.
• Followed CONTRIBUTING.md guidelines.