New field from upstream plugin: when the real client IP is
indeterminate (trusted proxy present but no usable XFF entry),
fail_closed=true blocks the request instead of passing it through.
- Add fail_closed to GeoBlockSettings type
- Include in mergeGeoBlockSettings (OR semantics: either global or host enables it)
- Emit fail_closed in buildBlockerHandler (only when true)
- Parse geoblock_fail_closed from form in both settings and proxy-host actions
- Add Checkbox UI in the Advanced accordion of GeoBlockFields
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>