Let plugins run their own PHP code

A plugin can now bring a plugin.php that registers hooks, scheduled tasks, its own tables, public pages and admin screens. Failures stay contained to the plugin; a form on a plugin page can be submitted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

config/services.yaml

@@ -30,7 +30,7 @@ services:
             tags: ['kant.task']
     App\:
         resource: '../src/'
-        exclude: '../src/{Kernel.php,Domain/}'
+        exclude: '../src/{Kernel.php,Domain/,Plugin/PluginApi.php,Plugin/PluginTask.php}'
     Doctrine\DBAL\Connection:
         factory: ['App\Infrastructure\ConnectionFactory', 'create']
         arguments: ['%env(projectdir:DATABASE_URL)%', '@App\Infrastructure\QueryCounter']
@@ -156,6 +156,7 @@ services:
         arguments:
             $tasks: !tagged_iterator kant.task
             $projectDir: '%kernel.project_dir%'
+            $plugins: '@App\Plugin\PluginRuntime'
     App\Ops\Zentrale:
         arguments:
             $root: '%kernel.project_dir%'