chore: add web toolchain and infrastructure for Plan 3

var/uploads/.htaccess

@@ -0,0 +1,2 @@
+Require all denied
+Deny from all

var/uploads/index.php

@@ -0,0 +1,7 @@
+<?php
+
+declare(strict_types=1);
+
+http_response_code(403);
+header('Content-Type: text/plain; charset=utf-8');
+echo "Forbidden\n";