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/redis-messenger/README.md

@@ -1,12 +0,0 @@
-Redis Messenger
-===============
-
-Provides Redis integration for Symfony Messenger.
-
-Resources
----------
-
- * [Contributing](https://symfony.com/doc/current/contributing/index.html)
- * [Report issues](https://github.com/symfony/symfony/issues) and
-   [send Pull Requests](https://github.com/symfony/symfony/pulls)
-   in the [main Symfony repository](https://github.com/symfony/symfony)