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/problems/classes/Problems/Permissions.php

@@ -1,48 +0,0 @@
-<?php
-
-namespace Grav\Plugin\Problems;
-
-use Grav\Plugin\Problems\Base\Problem;
-
-/**
- * Class Permissions
- * @package Grav\Plugin\Problems
- */
-class Permissions extends Problem
-{
-    public function __construct()
-    {
-        $this->id = 'Permissions Setup';
-        $this->class = get_class($this);
-        $this->order = -1;
-        $this->level = Problem::LEVEL_WARNING;
-        $this->status = false;
-        $this->help = 'https://learn.getgrav.org/troubleshooting/permissions';
-    }
-
-    /**
-     * @return $this
-     */
-    public function process()
-    {
-        if (PHP_OS_FAMILY === 'Windows') {
-            $this->msg = 'Permission check is not available for Windows.';
-            $this->status = true;
-            return $this;
-        }
-
-        umask($umask = umask(022));
-
-        $msg = 'Your default file umask is <strong>%s</strong> which %s';
-
-        if (($umask & 2) !== 2) {
-            $this->msg = sprintf($msg, decoct($umask), 'is potentially dangerous');
-            $this->status = false;
-        } else {
-            $this->msg = sprintf($msg, decoct($umask), 'looks good!');
-            $this->status = true;
-        }
-
-        return $this;
-    }
-}