feat(core): Change workflow deletions to soft deletes (#14894)

Adds soft‑deletion support for workflows through a new boolean column `isArchived`.

When a workflow is archived we now set `isArchived` flag to true and the workflows
stays in the database and is omitted from the default workflow listing query.

Archived workflows can be viewed in read-only mode, but they cannot be activated.

Archived workflows are still available by ID and can be invoked as sub-executions,
so existing Execute Workflow nodes continue to work. Execution engine doesn't
care about isArchived flag.

Users can restore workflows via Unarchive action at the UI.

packages/frontend/editor-ui/src/components/SetupWorkflowCredentialsButton/SetupWorkflowCredentialsButton.test.ts

@@ -31,6 +31,7 @@ const EMPTY_WORKFLOW = {
 	versionId: '1',
 	name: 'Email Summary Agent ',
 	active: false,
+	isArchived: false,
 	connections: {},
 	nodes: [],
 	usedCredentials: [],