fix: localizer fallback order

[nepinhum]

Description

• Align localizer fallback order with intended locale selection semantics.
• Preserve parent locale lookup for partial regional catalogs, e.g. es-MX falling back to es.
• Keep lower priority requested languages from being scanned after a preferred locale is selected.

Tests

• v test bundle_localizer_test.v
• v test .
• v fmt -verify localizer.v bundle_localizer_test.v