* feat: close modals with browser back button on mobile
Create reusable useModalHistory hook that pushes history state when a
modal opens and listens for popstate to close it. Apply to ReportModal,
ClearMissedConfirm, ExportModal, ImportConfirm, and all modals using
ConfirmModal/ShareDialog/Auth/ExportModal base components. Escape key
handling was already in place for desktop.
Closes#253
* fix: update tests for renamed button labels and missing useModalHistory mock
Daniel Volz