start articles require category routes, but the API has no direct endpoint for setting YRewrite fields

ich vermute, ich habe hier noch einen bug entdeckt beim befüllen von startartikeln:

aus dem Reasoning-Protokoll:

- Article 77 (bla) has startarticle: 1 — it IS a start article! So the metainfo endpoint blocks it.
- Article 73 (blubb) has startarticle: 0 — it's NOT a start article, and the metainfo endpoint WORKS.
- The metainfo data shows art_* fields but NOT yrewrite_title/yrewrite_description — those aren't in the registered metainfo fields.

Key issue: YRewrite SEO fields (yrewrite_title, yrewrite_description) are stored as columns in rex_article table but NOT registered as art_* metainfo fields.

All three target articles are start articles requiring category routes, but the API has no direct endpoint for setting YRewrite fields — neither the article metainfo endpoint nor the category metainfo endpoint handles yrewrite_* fields.