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/paquettg/string-encode/phpunit.xml

@@ -1,26 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<phpunit backupGlobals="false"
-	backupStaticAttributes="false"
-	bootstrap="phpunit.php"
-	colors="true"
-	convertErrorsToExceptions="true"
-	convertNoticesToExceptions="true"
-	convertWarningsToExceptions="true"
-	processIsolation="false"
-	stopOnFailure="false"
->
-	<testsuites>
-		<testsuite name="Repository Test Suite">
-			<directory>./tests/</directory>
-		</testsuite>
-	</testsuites>
-
-	<filter>
-		<whitelist addUncoveredFilesFromWhitelist="false">
-			<directory suffix=".php">src</directory>
-			<exclude>
-				<directory suffix=".php">vendor</directory>
-			</exclude>
-		</whitelist>
-	</filter>
-</phpunit>