feat: per-server notification thresholds with alert on agent metrics push

src/Core/Database.php

@@ -88,6 +88,11 @@ class Database
         return $this->query($sql, $params)->fetchAll();
     }
 
+    public function fetchCol(string $sql, array $params = []): array
+    {
+        return $this->query($sql, $params)->fetchAll(\PDO::FETCH_COLUMN);
+    }
+
     public function insert(string $table, array $data): int
     {
         $columns = implode(', ', array_keys($data));