xs: Add error message in homepage of dataset visualizer. (⚡️ UX Improvement)

[Jeerhz]

What this does

We verify the dataset endpoint before redirecting. When a user enters a dataset ID, a HEAD request is sent to check for the dataset’s existence. If the dataset isn’t found or if there is something wrong, an error message is shown:

How it was tested

• test_visualize_dataset is skipped.

How to checkout & try? (for the reviewer)

1. Start the development server.
2. Navigate to the homepage.
3. Enter a valid or invalid dataset ID in the input field and press Enter

Before

After

cc: @Pierre-LouisBJT