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/admin/tests/unit.suite.yml

@@ -1,9 +0,0 @@
-# Codeception Test Suite Configuration
-#
-# Suite for unit (internal) tests.
-
-class_name: UnitTester
-modules:
-    enabled:
-        - Asserts
-        - \Helper\Unit