chore: release prep — MIT badge, citation section, CITATION v0.4.0

- README: add MIT license badge, add ## Citation section
- inst/CITATION: bump version 0.2.0 → 0.4.0, add email/ORCID to author,
  add header field

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Refine eco-atlas extraction and distillation pipeline