perf(db): add missing indexes (appointment expiry, session dates, user status)

- appointments(status, expires_at): the per-minute expiry scheduler filtered on
  these with no covering index
- patient_sessions(created_at): dashboard revenue range scans
- users(status): admin user-list filter

PatientRecord(entity_type,entity_id) already covered by its unique constraint;
UserActiveContext.user_id is the PK — neither needed a new index.

src/Appointment/Entity/Appointment.php

@@ -12,6 +12,7 @@ use Symfony\Component\Uid\Uuid;
 #[ORM\Table(name: 'appointments')]
 #[ORM\Index(columns: ['doctor_id', 'slot_start'], name: 'idx_appointments_doctor_slot')]
 #[ORM\Index(columns: ['user_id', 'status'],       name: 'idx_appointments_user_status')]
+#[ORM\Index(columns: ['status', 'expires_at'],    name: 'idx_appointments_status_expires')]
 class Appointment
 {
     // Status machine: pending → confirmed → completed