feat: soft-delete for teamer accounts

addresses #869dv9br3

src/Repository/AvailabilityRepository.php

@@ -41,7 +41,12 @@ class AvailabilityRepository extends ServiceEntityRepository
         if (false === $custom) {
             $qb->andWhere($qb->expr()->isNull('availability.owner'));
         } else {
-            $qb->andWhere($qb->expr()->isNotNull('availability.owner'));
+            $qb
+                ->andWhere($qb->expr()->isNotNull('availability.owner'))
+                // a deleted teamer takes no further assignments, so their own
+                // availabilities must no longer be offered for disposition
+                ->andWhere($qb->expr()->isNull('teamer.deletedAt'))
+            ;
         }
 
         return $qb->getQuery();
@@ -49,6 +54,10 @@ class AvailabilityRepository extends ServiceEntityRepository
 
     public function getSelectableForTeamer(Teamer $teamer): array
     {
+        if (true === $teamer->isDeleted()) {
+            return [];
+        }
+
         $qb = $this->createQueryBuilder('availability');
 
         return $qb