fix(appointments): preload clinic + keep saved time on edit

The appointment-edit form opened with clinic/time blank even for
well-formed appointments because the pipeline never carried clinicId
end-to-end. Four-layer audit + fix:

1. APPOINTMENTS_QUERY now fetches clinicId + clinic { id clinicName }
   + doctor.fullName (was only doctor.id).
2. transformAppointments populates real clinicId + clinicName from the
   relation instead of faking clinicName=department.
3. Appointment type gets clinicId: string | null.
4. context-panel passes clinicId through to AppointmentForm's
   existingAppointment prop; form initial-states clinic from it.

Also on edit: if the saved timeSlot isn't in the fresh slot list
(past-slot filter, schedule change, clinic mismatch) we inject it as
"HH:MM (current)" so the dropdown displays the existing value instead
of looking cleared.

Historical appointments with clinicId=null on the platform still fall
through to the auto-select-from-slot logic; a maint backfill for those
is a separate task.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/types/entities.ts

@@ -323,6 +323,7 @@ export type Appointment = {
     patientId: string | null;
     patientName: string | null;
     patientPhone: string | null;
+    clinicId: string | null;
     clinicName: string | null;
 };