Function parseDateInputUnreviewed

Recognize a date from free-form text, or return null when it can't. Lenient by design (the field lets you type anything, then resolves on blur):

• ISO YYYY-MM-DD.
• Numbers in any separator, mapped to day/month/year by the locale's order — 06/07/2026 is June 7 in en-US, July 6 in de-DE.
• A month name plus a day and year (15 Jun 2026, June 15 2026).
• Eight run-together digits, split by the locale order (06152026 en-US).
• Two numbers (day + month) take the current year; two-digit years pivot at 70.

A real but out-of-[min, max] date returns null — the value stays uncommitted.