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/Service/DeckIntegrationService.php

@@ -60,7 +60,19 @@ class DeckIntegrationService {
 	 */
 	public function listBoardsForCurrentUser(): array {
 		$boards = $this->call(function () {
-			return $this->resolve(BoardService::class)->getUserBoards();
+			$boardService = $this->resolve(BoardService::class);
+			try {
+				// getUserBoards(?int $since, bool $includeArchived, …): with
+				// the default $includeArchived = true, Deck skips the
+				// `archived = false AND deleted_at = 0` conditions entirely,
+				// so archived *and* trashed boards come back. Ask for the
+				// filtered query instead of sorting them out afterwards.
+				return $boardService->getUserBoards(null, false);
+			} catch (Throwable $e) {
+				// Older/newer Deck with a different signature: fall back to
+				// the unfiltered call, isBoardHidden() below still filters.
+				return $boardService->getUserBoards();
+			}
 		}, []);
 
 		// Deck merges own/group/circle boards, so the same board can come