Improvement: Add transition to general hover states

[justinfar]

This is just a minor improvement, but it'd be great if we added a transition with duration-250 to elements with hover states (mostly buttons and icon buttons)

I'll likely expand on custom properties (exact duration, delay and animation specifics), and what specfically to add transitions to, when I work on creating more interactive components within Figma, but for now this would be a good first step to help the app feel a bit more snappier and polished.