When the Hashview server returns HTTP 200 with an error message and no
job_id (due to its internal notify_email bug), the CLI and interactive
paths now:
- exit 1 (not 0) in the CLI path
- print "✗ Error" instead of "✓ Success"
- print a hint to check the Hashview UI before retrying, preventing
duplicate job creation
Adds test for the error response path in test_cli_flags.py.