fix(clients): purge depleted clients by their exact usage key

DelDepleted turned the emails of depleted usage rows into client
identities through BulkDelete, which trims each email for request
bodies. A depleted row keyed by a padded email, which a node's stats
could store and which belongs to no client, therefore resolved to the
healthy client it resembled and deleted it. Rows whose key carries
surrounding white space name no client and are skipped.

internal/web/service/client_bulk.go

@@ -1533,8 +1533,9 @@ func (s *ClientService) DelDepleted(inboundSvc *InboundService) (int, bool, erro
 
 	seen := make(map[string]struct{}, len(rows))
 	emails := make([]string, 0, len(rows))
+	// BulkDelete trims each email, so a padded usage row would resolve to the client it resembles.
 	for _, r := range rows {
-		if r.Email == "" {
+		if r.Email == "" || r.Email != strings.TrimSpace(r.Email) {
 			continue
 		}
 		if _, ok := seen[r.Email]; ok {