Add Deck workflow automation Nextcloud app

Ports the standalone due-date cron script into a proper Nextcloud 34
app with a personal-settings UI, per-user workflow configuration
(source/target stack, assigned-user and label filters, email
notification), a TimedJob background runner, and Gitea CI pipelines.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/BackgroundJob/RunWorkflowsJob.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\WorkflowDeckAutomation\BackgroundJob;
+
+use OCA\WorkflowDeckAutomation\Service\WorkflowRunner;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\IJob;
+use OCP\BackgroundJob\TimedJob;
+
+class RunWorkflowsJob extends TimedJob {
+	public function __construct(
+		ITimeFactory $time,
+		private WorkflowRunner $runner,
+	) {
+		parent::__construct($time);
+		$this->setInterval(5 * 60);
+		$this->setTimeSensitivity(IJob::TIME_INSENSITIVE);
+		$this->setAllowParallelRuns(false);
+	}
+
+	protected function run($argument): void {
+		$this->runner->run();
+	}
+}