Move plugins to manifest, pin Docker version, add Makefile

- Add plugins.txt listing all plugins for reproducible installs
- Add Makefile with setup/start/stop/install-plugins targets
- Remove user/plugins/ from git tracking
- Pin Docker image to 1.7.49.5-ls244

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/email/vendor/symfony/messenger/Middleware/FailedMessageProcessingMiddleware.php

@@ -1,36 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\Messenger\Middleware;
-
-use Symfony\Component\Messenger\Envelope;
-use Symfony\Component\Messenger\Stamp\ReceivedStamp;
-use Symfony\Component\Messenger\Stamp\SentToFailureTransportStamp;
-
-/**
- * @author Ryan Weaver <ryan@symfonycasts.com>
- */
-class FailedMessageProcessingMiddleware implements MiddlewareInterface
-{
-    public function handle(Envelope $envelope, StackInterface $stack): Envelope
-    {
-        // look for "received" messages decorated with the SentToFailureTransportStamp
-        /** @var SentToFailureTransportStamp|null $sentToFailureStamp */
-        $sentToFailureStamp = $envelope->last(SentToFailureTransportStamp::class);
-        if (null !== $sentToFailureStamp && null !== $envelope->last(ReceivedStamp::class)) {
-            // mark the message as "received" from the original transport
-            // this guarantees the same behavior as when originally received
-            $envelope = $envelope->with(new ReceivedStamp($sentToFailureStamp->getOriginalReceiverName()));
-        }
-
-        return $stack->next()->handle($envelope, $stack);
-    }
-}