chore: snapshot notifications hardening and css/docs alignment

lib/Repository/Tenant/UserTenantRepository.php

@@ -85,6 +85,33 @@ class UserTenantRepository implements UserTenantRepositoryInterface
         return $result;
     }
 
+    /** @return list<int> */
+    public function listActiveUserIdsByTenantId(int $tenantId): array
+    {
+        if ($tenantId <= 0) {
+            return [];
+        }
+
+        $rows = DB::select(
+            'select ut.user_id from user_tenants ut join users u on u.id = ut.user_id and u.active = 1 where ut.tenant_id = ?',
+            (string) $tenantId
+        );
+
+        if (!is_array($rows)) {
+            return [];
+        }
+
+        $ids = [];
+        foreach ($rows as $row) {
+            $data = $row['user_tenants'] ?? $row;
+            if (is_array($data) && isset($data['user_id'])) {
+                $ids[] = (int) $data['user_id'];
+            }
+        }
+
+        return array_values(array_unique($ids));
+    }
+
     private function extractIntField(array $row, string $field): int
     {
         foreach ($row as $value) {