feat: external HTTPS monitoring pull via monitor.php

Add cron-ready pull checks for critical URLs with SSL expiry warnings,
retry-before-alert, JSON results in private/data, email alerts, and a
90-day target-list review reminder.

Co-authored-by: Cursor <cursoragent@cursor.com>

public/monitor.php

@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * External HTTPS/SSL monitoring — run via Plesk cron or CLI.
+ * Usage: php monitor.php [--verbose]
+ */
+
+$configDir = is_dir(dirname(__DIR__) . '/private/config')
+    ? dirname(__DIR__) . '/private/config'
+    : dirname(__DIR__) . '/config';
+
+require_once $configDir . '/monitor-lib.php';
+
+set_time_limit(300);
+
+$verbose = in_array('--verbose', $argv ?? [], true);
+exit(runMonitor($verbose));