Server: stop a team being archived while a vault is created in it

src/DodoSSH.Api/Features/Teams/TeamService.cs

@@ -255,16 +255,6 @@ internal sealed class TeamService(
             throw new InvalidOperationException("Only the owner of a team can archive it.");
         }
 
-        var vaultCount = await CountVaultsAsync(team.Id, cancellationToken).ConfigureAwait(false);
-
-        if (vaultCount > 0)
-        {
-            throw new TeamNotEmptyException(
-                string.Create(
-                    CultureInfo.InvariantCulture,
-                    $"This team still owns {vaultCount} vault(s), and archiving it would take them away from everybody holding a key — including you. Delete those vaults first, which asks about each one and withdraws every key to it."));
-        }
-
         var now = clock.GetUtcNow();
         var archived = await database.ExecuteFreshAsync([team], async () =>
         {
@@ -273,6 +263,19 @@ internal sealed class TeamService(
                 .ConfigureAwait(false);
             await using var _ = transaction.ConfigureAwait(false);
 
+            // Counted under the lock a vault create takes, so one cannot land between this and the archive.
+            await TeamLock.AcquireAsync(database, team.Id, cancellationToken).ConfigureAwait(false);
+
+            var vaultCount = await CountVaultsAsync(team.Id, cancellationToken).ConfigureAwait(false);
+
+            if (vaultCount > 0)
+            {
+                throw new TeamNotEmptyException(
+                    string.Create(
+                        CultureInfo.InvariantCulture,
+                        $"This team still owns {vaultCount} vault(s), and archiving it would take them away from everybody holding a key — including you. Delete those vaults first, which asks about each one and withdraws every key to it."));
+            }
+
             var memberships = await database.TeamMemberships
                 .Where(m => m.TeamId == team.Id && m.DeletedAtUtc == null)
                 .ToListAsync(cancellationToken)