feat(FN-2721): enforce node override guard across task workflows

- Add a core node-override-guard module, export it from @fusion/core, and enforce conflicts in store updates
- Add API route and CLI extension safeguards so nodeId override updates are blocked when ownership would conflict
- Wire node override routing and validation through dashboard quick-create, list, modal, settings, and task form/detail surfaces
- Add focused unit and integration tests for core guard logic, workflow routes, and dashboard node override UX

packages/dashboard/app/components/QuickEntryBox.css

@@ -117,6 +117,15 @@
   position: relative;
 }
 
+.quick-entry-node-wrap {
+  display: inline-flex;
+  align-items: center;
+}
+
+.quick-entry-node-select {
+  max-width: 250px;
+}
+
 .quick-entry-subtasks-toggle {
   display: inline-flex;
   align-items: center;