CVE-2026-29090: Rucio SQL injection in postgres_meta DID search path compromises PostgreSQL metadata database

### Summary A SQL injection vulnerability exists in Rucio versions 1.30.0 and later before 35.8.5, 38.5.5, 39.4.2, and 40.1.1, in `FilterEngine.create_postgres_query()`. This allows any authenticated Rucio user to execute arbitrary SQL against the PostgreSQL metadata database through the DID search endpoint (`GET /dids/<scope>/dids/search`). When the `postgres_meta` metadata plugin is configured, attacker-controlled filter keys and values are interpolated directly into raw SQL strings via Python `.format()`, then passed to `psycopg3`'s `sql.SQL()` which treats the string as trusted SQL syntax. Depending on the database privileges assigned to the service account, exploitation can expose sensitive tables, modify or delete metadata, access server-side files, or achieve code execution through PostgreSQL features such as COPY ... FROM PROGRAM. This issue affects deployments that explicitly use the postgres_meta metadata plugin. This vulnerability has been fixed in versions 35.8.5, 38.5.5, 39.4.2, and 40.1.1.