OnboardingOverlay could reappear for already-onboarded users when the
core config RPC call failed (sidecar not ready, timeout). The catch block
hardcoded `false`, ignoring the persisted Redux `isOnboardedByUser` flag.
Now reads `selectIsOnboarded` as a fallback in the catch block and combines
both flags in shouldShow — either being true prevents the overlay. Also fixes
DEV_FORCE_ONBOARDING which was a no-op (identical ternary branches).
Closes#197