feat: add tooltips for icon buttons
Conflicts came from the branch predating the Pro banner work and the deleted
API key step. Resolved by keeping master's `onEdit` on the user actions popup
and wrapping it in the tooltip, and by leaving `ApiKeyStep.jsx` deleted.
The `switchToView` key is dropped in favour of one complete string per view.
Interpolating a view name into "Switch to {{view}} view" required
`t('common.' + view).toLowerCase()` at the call site, and lowercasing a
translated string is wrong wherever case carries meaning: German capitalises
nouns, and Turkish turns I into a dotless ı. The five replacements need no
interpolation and no lowercasing.
Daniel Hiller