A rejected Hardcover token is retried on every call during a bulk import #3101

Problem

Follow up to #2075. With a Hardcover token configured but rejected (expired or revoked), every metadata call during a bulk import still sends one request to Hardcover and gets a 401. #2082 fixed the case with no token at all, and #3100 adds retries and shared backoff for rate limits, but a rejected token is neither: it fails fast, once per call, for the whole import.

Proposed solution

Treat a 401 from Hardcover as "Hardcover is off for the rest of this operation" (a bulk import run, a discovery sweep), log it once with a clear message pointing at Settings, and surface it in the import result and the Hardcover settings health. Resume normal behaviour on the next operation or when the token is changed.

Build after #2699, which changes the same request loop for the daily quota.

Refs #2075, #3100.