2.0.23: Localize validator attribute names for admin Livewire screens

Add a shared HasValidationLabels trait (AdminShell/Infrastructure) that maps
each validation rule key to the existing v1 language key its form label uses,
via validationAttributes()/messages(). Validation errors now read the real
field name in the active locale instead of leaking raw Livewire state paths
(e.g. "form.name", "newForm.code"). No new language keys are introduced.

Applied to the custom-field, home-layout, language, language-string, menu,
permission, role, user and api-connection screens. Screens with their own
messages() (permission/role/user) merge via localizedRuleMessages().

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>