GHSA-gj6x-q8rh-wj6x: Curio exposes database credentials to users with network access through verbose HTTP error responses

Multiple HTTP handlers in Curio passed raw database error messages to HTTP clients via http.Error(). When the PostgreSQL/YugabyteDB driver (pgx) returned errors, these could contain the database connection string — including hostname, port, username, and password. Additionally, the internal connection string was constructed with the plaintext password embedded in the URL, which was also included in startup error messages and could surface in logs.