The IANA picker was an <input list=datalist>, which filters the dropdown by
whatever text is already in the field — so with the stored zone pre-filled a
user only saw a single option and had to erase the value (undiscoverable) to
browse. datalist is also unreliable in iOS Safari.
Replace it with a native <select> grouped by region (<optgroup>): tapping
shows the whole list with no typing/erasing, and it renders as the native
wheel picker on iOS. The "Use detected" one-tap shortcut still covers the
common case. Option labels are shortened (region stripped, underscores → spaces)
while values remain full IANA ids. e2e updated from fill() to selectOption().
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
