QJob into JobV1

[JooNiv]

QJob is now a Qiskit JobV1

closes #28

Why

QBackendIQM subclasses IQMBackend, so consumers treat the return value of run() as a
qiskit.providers.JobV1. QJob was a plain class with job_id as an int attribute and
status() returning a string. That made job.job_id() raise TypeError and made every
JobStatus based poll loop never terminate, silently. It broke e.gfiqci-ems and would break
any other Qiskit facing consumer or package trying to integrate with Qiskit or IQM software stack.

What changed

QJob derives from JobV1. status() returns a JobStatus, and submit() and cancel()
were added, so done(), cancelled(), in_final_state() and wait_for_final_state() all
work. HEAppE_QISKIT_STATUS_MAPPING holds JobStatus members now. WAITING still maps to
RUNNING rather than QUEUED, which is left as a separate change.

job_id stays an int through a callable int subclass, so job.job_id is still e.g. int 1234 for
QClient calls and HEAppE result paths while job.job_id() returns e.g. str '1234' for Qiskit.
That keeps every existing reader of job.job_id working.

Cancelling a job used to report JobStatus.ERROR, with two causes. QClient.get_job_status
folded JobState.Canceled into FAILED, so it now returns a distinct CANCELED, and the
four poll loops stop on QClient.TERMINAL_JOB_STATES instead of a local list. That is not
enough on its own, because HEAppE reaps a cancelled job as JobState.Failed and never as
Canceled. So cancel() records that HEAppE accepted the request, and _to_qiskit_status()
reports CANCELLED rather than ERROR when it did. A job cancelled out of band still
reports ERROR, which is documented on the method.

backend_service.py compared job.status() against IQMJobStatus, but IQMJob.status()
returns a Qiskit JobStatus, so that operand was always false and remote failure detection
rested on not result.success alone. It now compares against JobStatus.ERROR.

Cancel on timeout in result() and wait_for_final_state() called
self._backend.cancel_job(...), which raised AttributeError after the first result()
because update_from_remotejob() replaces self._backend. Both call self.cancel() now.

Verified on VLQ

• returned job now bahaves like a JobV1
• job.job_id gives 1234 and job.job_id() gives '1234'
• status() returns the same value before and after the first result(), and done() and
  in_final_state() are true once results are in
• after cancel(), HEAppE reports JobState.Failed and job.status() gives
  JobStatus.CANCELLED
• fiqci-ems works as expected on VLQ (used as an integration test)