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/automagic-images/vendor/guzzlehttp/guzzle/vendor-bin/php-cs-fixer/composer.json

@@ -1,9 +0,0 @@
-{
-    "require": {
-        "php": "^7.2.5 || ^8.0",
-        "friendsofphp/php-cs-fixer": "2.18.3"
-    },
-    "config": {
-        "preferred-install": "dist"
-    }
-}

plugins/automagic-images/vendor/guzzlehttp/guzzle/vendor-bin/phpstan/composer.json

@@ -1,10 +0,0 @@
-{
-    "require": {
-        "php": "^7.2.5 || ^8.0",
-        "phpstan/phpstan": "0.12.81",
-        "phpstan/phpstan-deprecation-rules": "0.12.6"
-    },
-    "config": {
-        "preferred-install": "dist"
-    }
-}

plugins/automagic-images/vendor/guzzlehttp/guzzle/vendor-bin/psalm/composer.json

@@ -1,9 +0,0 @@
-{
-    "require": {
-        "php": "^7.2.5 || ^8.0",
-        "psalm/phar": "4.6.2"
-    },
-    "config": {
-        "preferred-install": "dist"
-    }
-}