Add 404 page

[panvicka]

Story

As a user, I want to see a meaningful and visually appealing 404 page, so that I can understand when a requested page is not found and navigate back to the app seamlessly.

Scenario

Given I am using the app,
When I enter an incorrect or non-existent URL,
Then I should be redirected to the 404 page.

Acceptance Criteria:

• The 404 page should have a clear and user-friendly design that aligns with the app's visual theme.
• The 404 page should be responsive and work well on various screen sizes and devices.