[BUG] Use actual localization for birth date input?

[ghbrown]

The localization for the date of birth (DOB) on the registration screen can only be one of two options (de or en-GB).
I wasn't paying much attention and tried to use MM/DD/YYYY, and was surprised when the date changed with no explanation.

To Reproduce

• go to Alovoa and try to register with email
• try to enter a MM/DD/YYYY format date and watch it change (e.g. 08/30/2000 -> 08/08/2001 on last keystroke)

Expected behavior

The date format should respect the actual localization, here en-US would suffice for me.

Web application

(though I suspect iOS and Android are affected too)

• Firefox 129

Proposed fix

• replace locale={getDateInputLocale()} with locale={Localization.locale} on this line
• delete getDateInputeLocale() which is no longer used

This fix works locally for the web version, but I can't guarantee much more than that.
I'm sure this is/was related to the only two translations being de and en, but this is the only place in the code I've found something like this being done and I don't immediately see how this change would break things.

If this fix is acceptable I am happy to make a PR.

[Nonononoki]

The locale is limited to de and en right now because those are the supported languages.

[ghbrown]

The fact that MM/DD/YYYY is impossible for en-US even though English is a supported language seems like a bug. My proposal is one way to address this, but another approach may be preferable.

My proposed fix should allow date input in any localization, even if their local language is not supported by an internationalization file since this change only affects the date picker. I don't see any real downsides.