Add Names() and LoadInsensitive() for case-insensitive timezone lookup

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Add zone metadata: country codes/names and coordinates

Parse zone1970.tab and iso3166.tab (now included in the embedded zip)
to expose per-zone metadata via Zone.Meta(): ISO 3166 country codes
and names, lat/lon coordinates, and optional commentary.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Fix unused variable warning in ParsePosixTZ

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>