DateTimeInput date parsing is not great.

The Date parsing on the DateTimeInput is not super flexible and because of how browsers work, may "clear" values when rendering them.

Our basic catalog implementation should be a little bit more [robust](https://github.com/a2ui-project/a2ui/blob/main/renderers/angular/src/v0_9/catalog/basic/date-time-input.component.ts#L108-L118) [than](https://github.com/a2ui-project/a2ui/blob/main/renderers/lit/src/v0_9/catalogs/basic/components/DateTimeInput.ts#L31-L52) [this](https://github.com/a2ui-project/a2ui/blob/main/renderers/react/src/v0_9/catalog/basic/components/DateTimeInput.tsx#L22-L40).

There's some cool libraries that we could use (like `any-date-parser` backed by Intl?), but as an MVP, we should guarantee that we can parse exactly what the spec says (and add tests to prove it)