chore: refresh OECD DAC area codelists

[github-actions]

Automated refresh of the DAC area codelists from the live OECD source
(development-finance-codelists.oecd.org).

This PR exists because the committed dac{1,2}_codes_area.json are out of
date with the live codelists. Review the diff before merging:

• Added codes are new active DAC areas — confirm they look legitimate.
• Changed values are codes whose .stat (dotstatcode) was updated
  upstream — confirm the change is intended (these affect translation output).
• Historical codes are preserved (never deleted), so old data still translates.

Merging runs the normal CI suite. If nothing here looks right, close the PR
and investigate the source rather than merging.