Fix:Error message for invalid task ID

[rahul-flex]

Previously, when web.load received a 404 response for an invalid or non-existent task ID, the client would return None and produce unhelpful error messages. This commit changes that behavior: it now raises a TaskNotFoundError with a clear, user-friendly explanation.

[yaugenst-flex]

Thanks @rahul-flex! This is going in the right direction but we should try to handle 404 errors more generally.

[rahul-flex]

Updated error message:

[yaugenst-flex]

Closes #2154

[yaugenst-flex]

Thanks @rahul-flex looks good to go from my side, minus the little changelog clarification.

[yaugenst-flex]

@QingengWei could you have a look? This addresses the discussion in #2154. The http_interceptor now raises an error on 404 instead of returning None, which means that the API should now be able to return 404 status which we then need to handle properly here on the client.

The old if resp is None checks are still in place to keep compatibility but I think we should move to returning "normal" status codes on the API side?

[yaugenst-flex]

@rahul-flex I think this is good to go after the small change in the changelog. could you rebase?