feat: add app and database modules

app/Exceptions/MonitoringException.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exceptions;
+
+use RuntimeException;
+
+class MonitoringException extends RuntimeException
+{
+    public static function unsupportedOs(string $os): self
+    {
+        return new self("Monitoring is not implemented for OS family: {$os}");
+    }
+
+    public static function probeFailed(string $probe, string $reason): self
+    {
+        return new self("Probe '{$probe}' failed: {$reason}");
+    }
+}