Auth Web Centralize Tooltip CSS

## What is the problem?
* Currently all of the v-tooltips are using a custom css tooltip design which is implemented independently for each component that uses it.

## What is the impact?
* There is lots of repeated css across auth-web and it takes longer to implement a new v-tooltip to the custom design.

## Proposed solution
* Centralize the tooltip css (ie, in `base.scss`) so each new tooltip has the same design. Similar to v-btn.

## Note
* It might be worth it to look at other repos as well as this tooltip design is widely used e.g. Namerequest

Start by locating the independent v-tooltip styles in auth-web and reviewing base.scss, then compare the tooltip design with related repositories such as Namerequest. Done means the repeated tooltip CSS is centralized and new v-tooltips use the same design without component-specific copies.

Written by the indexing model from the issue text.