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/AppInfo/Application.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\WorkflowDeckAutomation\AppInfo;
+
+use OCP\AppFramework\App;
+use OCP\AppFramework\Bootstrap\IBootContext;
+use OCP\AppFramework\Bootstrap\IBootstrap;
+use OCP\AppFramework\Bootstrap\IRegistrationContext;
+
+class Application extends App implements IBootstrap {
+	public const APP_ID = 'workflow_deck_automation';
+
+	public function __construct() {
+		parent::__construct(self::APP_ID);
+	}
+
+	public function register(IRegistrationContext $context): void {
+	}
+
+	public function boot(IBootContext $context): void {
+	}
+}