feat: ssh auth, protocol management, and cleanup

inc/Logger.php

@@ -0,0 +1,25 @@
+<?php
+
+class Logger {
+    private const DEFAULT_LOGS_DIR = __DIR__ . '/../logs';
+
+    private static function ensureDir(string $dir): void {
+        if (!is_dir($dir)) {
+            @mkdir($dir, 0777, true);
+        }
+    }
+
+    private static function getLogsDir(): string {
+        // Fallback to project logs directory next to inc/
+        $dir = self::DEFAULT_LOGS_DIR;
+        self::ensureDir($dir);
+        return $dir;
+    }
+
+    public static function appendInstall(int $serverId, string $message): void {
+        $dir = self::getLogsDir();
+        $file = $dir . '/install_server_' . $serverId . '.log';
+        $line = '[' . date('Y-m-d H:i:s') . '] ' . $message . "\n";
+        @file_put_contents($file, $line, FILE_APPEND);
+    }
+}