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/WorkflowSettings.test.ts

@@ -60,6 +60,7 @@ describe('WorkflowSettingsVue', () => {
 				id: '1',
 				name: 'Test Workflow',
 				active: true,
+				isArchived: false,
 				nodes: [],
 				connections: {},
 				createdAt: 1,
@@ -71,6 +72,7 @@ describe('WorkflowSettingsVue', () => {
 			id: '1',
 			name: 'Test Workflow',
 			active: true,
+			isArchived: false,
 			nodes: [],
 			connections: {},
 			createdAt: 1,
@@ -273,6 +275,7 @@ describe('WorkflowSettingsVue', () => {
 			id: '1',
 			name: 'Test Workflow',
 			active: true,
+			isArchived: false,
 			nodes: [],
 			connections: {},
 			createdAt: 1,