A partial date (e.g. "14.03.") left the hidden ISO input empty, so
saving the edit form silently cleared a stored date. PersonLifeDateField
now delegates to the shared DateInput primitive (inline format error,
calendar validation) and sets a custom validity while the error is
present, so the browser blocks native submission for both person forms.
A full clear stays submittable - that is the intentional clear path.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>