refactor: replace intersection observer in board

[Schwehn42]

Description

Replaces the intersection observer used to determine whether the board is scrollable and which column to show. Reasons:

1. this is part of a larger refactor of the board and column component
2. the code was clunky
3. using a hook is more readable and reusable
4. the tests wouldn't work with a higher TS version so not requiring them keeps us out of trouble

Changelog

• add hook useIsTouchingSides
• remove IntersectionObserver and all surrounding logic from Board
• change board scroll logic

Checklist

• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] The application was tested in the most commonly used browsers (e.g. Chrome, Firefox, Safari)