Issue with openeuler source returning 404

Currently the openeuler REST source supplies some vulnerability IDs via their all.json, but some records return 404 when we try to retrieve them.

E.g.
- https://repo.openeuler.org/security/data/osv/OESA-2026-3208.json
- https://repo.openeuler.org/security/data/osv/OESA-2026-3212.json

Start by reproducing the 404 responses for OESA-2026-3208.json and OESA-2026-3212.json, then trace how the openeuler REST source consumes all.json and retrieves individual records. Done means the source handles these records without failing on 404 responses, with the relevant behavior covered by the project's tests.

Written by the indexing model from the issue text.