Update landing page to use bootstrap instead of tailwind

[Sukhpreet-s]

Resolves #4395

Description

This PR updates the landing_page to use Bootstrap instead of Tailwind. This is to avoid the usage of 2 different UI libraries across the application and since tailwind is only used for this landing page and bootstrap can be easily utilized for this task.

The landing_page.scss is updated by removing the old styles, which were not being used at all, and adding new styles.

The flash message is updated to use shared/_flash and the file shared/_flash_tailwind.html.erb is removed.

Some decisions that are made:

• The landing_page.scss stylesheet is used instead of the application.scss to avoid loading the unnecessary massive amount of css code just for the main page. Instead, bootstrap is imported into the landing_page.scss.
• The CDN for Alpine.js is removed since it is not used anywhere on the page. The dropdown code that was using it was removed in an older PR.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Manually by testing all the buttons on the page, and visually checking for any styling issue including responsive design issues.

Screenshots

After

Before

Flash messages (Not sure how the flash messages are used on this page but this example is done by manually setting the flash message for testing purposes just to show how they look)

[dorner]

No worries on technical side - over to @cielf to make sure the landing page still looks good.

[cielf]

LGTM!

[github-actions]

@Sukhpreet-s: Your PR Update landing page to use bootstrap instead of tailwind is part of today's Human Essentials production release: 2025.02.09.
Thank you very much for your contribution!