fix: decouple php-fpm reload from HTTP request using flag file + cron

Reload during account creation was causing 502 by killing the fpm worker
before nginx finished reading the response. Flag file picked up by cron
within 60s instead.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LP9Q4kfCAYAjJnsbHBrViZ

panel/lib/PHPManager.php

@@ -118,8 +118,8 @@ php_value[max_execution_time]  = 30
     }
 
     private static function reloadFPM(string $ver): void {
-        // Run reload in background so it doesn't block/kill the current PHP-FPM worker.
-        // The short sleep ensures the pool config is fully written before reload picks it up.
-        exec("(sleep 1 && sudo systemctl reload php{$ver}-fpm) </dev/null >/dev/null 2>&1 &");
+        // Write a flag file instead of reloading inline — the cron runner picks this up
+        // within 60s and reloads fpm outside of any HTTP request, avoiding 502s.
+        @file_put_contents('/tmp/novacpx-fpm-reload-' . $ver, '1');
     }
 }