Function process_one 

async fn process_one(
    client: &Client,
    pool: &PgPool,
    config: &RdioConfig,
    row: StreamRow,
)

Uploads a single stream and records the outcome.

Errors from either the HTTP upload or the status-transition query are logged but never propagated — the caller iterates over a batch and we do not want one bad row to abort the rest.