Hide inactive boards, keep source and target stack apart, make the interval configurable

- Boards: BoardService::getUserBoards() defaults to $includeArchived = true,
  and that flag also gates the `deleted_at = 0` condition, so archived and
  trashed boards showed up in the dropdown. Request the filtered query
  instead, with a fallback to the no-arg call if the signature ever changes.
  Stacks need nothing: StackMapper::findAll() always filters deleted_at.
- Each stack dropdown now hides whatever the other one holds, so source and
  target can no longer be set to the same stack. The save-time check stays
  as the backstop for rows stored before this rule.
- RunWorkflowsJob reads its interval from config.php
  ('workflow_deck_automation.interval', seconds, default 300, clamped to a
  60s minimum). TimedJob re-reads the interval on every cron pass, so a
  changed value takes effect without any occ command.

lib/BackgroundJob/RunWorkflowsJob.php

@@ -8,18 +8,42 @@ use OCA\WorkflowDeckAutomation\Service\WorkflowRunner;
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\BackgroundJob\IJob;
 use OCP\BackgroundJob\TimedJob;
+use OCP\IConfig;
 
 class RunWorkflowsJob extends TimedJob {
+	/**
+	 * config.php key holding how often (in seconds) workflows are checked.
+	 */
+	public const INTERVAL_CONFIG_KEY = 'workflow_deck_automation.interval';
+
+	public const DEFAULT_INTERVAL = 5 * 60;
+
+	/**
+	 * Nextcloud's cron itself only ticks every 5 minutes by default, so
+	 * anything below a minute would only add load without running more
+	 * often. Values under this are clamped rather than rejected.
+	 */
+	public const MINIMUM_INTERVAL = 60;
+
 	public function __construct(
 		ITimeFactory $time,
+		IConfig $config,
 		private WorkflowRunner $runner,
 	) {
 		parent::__construct($time);
-		$this->setInterval(5 * 60);
+		// TimedJob compares against this value on every cron pass, so a
+		// changed config.php takes effect on the next pass — no occ command
+		// and no re-registration of the job needed.
+		$this->setInterval(self::resolveInterval($config));
 		$this->setTimeSensitivity(IJob::TIME_INSENSITIVE);
 		$this->setAllowParallelRuns(false);
 	}
 
+	private static function resolveInterval(IConfig $config): int {
+		$interval = $config->getSystemValueInt(self::INTERVAL_CONFIG_KEY, self::DEFAULT_INTERVAL);
+		return max(self::MINIMUM_INTERVAL, $interval);
+	}
+
 	protected function run($argument): void {
 		$this->runner->run();
 	}