Created Title Banner

[Danyon-Talbot]

This PR adds a banner across the top of the page displaying a welcome message.

To achieve this, there had to be some HTML reorganisation.

• The Header is now separate from the "main" section of HTML.
• The "h3" header element has been moved into "searchContainer".

CSS:

• Added CSS for several elements to override Tailwind's default stylings.

JS:

• This PR also includes the bugfix for the Hide button's page layout issues.
• This is also pushed in a separate PR, and is pending review there. I included it here to push this code with proper functionality.

I have colour coded various elements for my personal ease of use with styling. These are temporary.