feat(resource): ad-hoc blocking, 409 recovery, and the rest of the flake

Ad-hoc resource blocking
- "The laser is being serviced this afternoon" is a specific range, not a change
  to the resource's working pattern. It stays separate from calendar exceptions
  and the modal says which is which — merging them means either an afternoon's
  closure lives in the calendar forever, or a change to working hours vanishes
  with one click
- Blocking a range that already holds an appointment is refused with 409 rather
  than silently taking capacity back; the appointment is still there and someone
  has to decide about it first
- Deleting an occupancy that belongs to an appointment is refused too, otherwise
  a patient's booking would quietly lose its resource with no record

409 on hold now recovers
Saying "someone just took it" is not enough — the operator would have to search
again by hand. The page drops the stale selection and refetches, so alternatives
are on screen immediately.

Flake, second half
The earlier fix only covered createUser's retry path. Any test that trips a
unique constraint closes the EntityManager, and the next test inherits the same
closed instance from the container. setUp now resets the registry when it finds
a closed manager, so a test's starting state no longer depends on how the
previous one failed.

Three consecutive full runs green: 1340 tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/Appointment/Availability/Controller/AvailabilityController.php

@@ -41,7 +41,6 @@ class AvailabilityController extends BaseController
         private readonly DoctorRepository         $doctors,
         private readonly BranchResolver           $branches,
         private readonly \App\Course\Repository\TreatmentCourseRepository $courses,
-        private readonly \App\Appointment\Availability\Picker\ResourcePickerRegistry $pickers,
     ) {}
 
     #[Route('/api/v1/appointment-availability', name: 'appointment_availability', methods: ['POST'])]