Tie workflows to the board owner instead of their creator

A workflow now belongs to whoever owns its board. The settings page
lists, edits and deletes workflows by board ownership alone, using
Deck's BoardMapper::findAllByOwner(), a single owner query that never
returns shared boards and carries no frozen uid. A transferred board's
workflows therefore show up for the new owner immediately.

The background job still needs one user to run as and mail, so it
looks up the board owner before every run and stores it in user_id
when it changed. Archived boards stay listed so their workflows keep
a name, but are no longer offered or accepted as a target.

src/PersonalSettings.vue

@@ -175,8 +175,10 @@ const loadedBoardId = ref(null)
 
 const collator = new Intl.Collator(undefined, { numeric: true, sensitivity: 'base' })
 
-// The backend only returns boards the user owns.
+// The backend only returns boards the user owns. Archived ones are in there
+// so their workflows keep a board name, but are no target for new ones.
 const boardOptions = computed(() => boards.value
+	.filter((board) => !board.archived || board.id === form.boardId)
 	.map((board) => ({ value: board.id, label: board.title }))
 	.sort((a, b) => collator.compare(a.label, b.label)))
 
@@ -230,7 +232,7 @@ const workflowIssues = computed(() => {
 
 	for (const workflow of workflows.value) {
 		if (!boards.value.some((board) => board.id === workflow.boardId)) {
-			issues[workflow.id] = 'Board nicht mehr vorhanden oder nicht dein eigenes'
+			issues[workflow.id] = 'Board nicht mehr vorhanden'
 			continue
 		}