Improve coverage of Amount component

[Anny]

There is a mix of <Amount/> components and manual {{ formatCurrency(amount) }} calls in modals. Ideally all monetary values should be represented through the component, but it has scoped styles that affect appearance when misused.

Some possible approaches:

• Add a flag to the component to disable styling (I experimented with a sub boolean to toggle sub/span with unsatisfactory results)
• Remove styling from the component and reapply in parent component where appropriate
• Just don't, and say we did

[Anny]

Additionally, the component should handle different types of value as follows:

• undefined -> placeholder value (currently "...")
• NaN -> emdash placeholder (—)
• String -> as-is (assumed preformatted)
• Number -> per current implementation