feat(FN-1862): add completion state tracking for onboarding

- Add markOnboardingCompleted() to set completedAt timestamp when user finishes onboarding
- Add isOnboardingCompleted() to check if onboarding was completed (vs dismissed)
- Update ModelOnboardingModal to call markOnboardingCompleted on successful completion
- Skip onboarding auto-open when already completed locally
- Add completion state tracking tests in ModelOnboardingModal.test.tsx
- Add model-onboarding-state unit tests
- Update useAuthOnboarding to check local completion state before auto-opening
- Document localStorage completion state tracking pattern in .fusion/memory.md

packages/dashboard/app/components/AddNodeModal.tsx

@@ -109,7 +109,7 @@ export function AddNodeModal({ isOpen, onClose, onSubmit, addToast }: AddNodeMod
 
     try {
       await onSubmit(input);
-      addToast(`Node "${input.name}" registered`, "success");
+      addToast(`Node \"${input.name}\" registered`, "success");
       closeModal();
     } catch (error) {
       const message = error instanceof Error ? error.message : "Failed to register node";