shawn
6c1d5c3910
feat: add comprehensive empty states & onboarding
- Enhanced empty-state design pattern (icon + heading + description + CTA)
- Customers: 'No Customers Yet' with Add Customer CTA
- Locations: 'No Locations Yet' with Add Location CTA
- Dashboard: Full empty state when no assets exist, preserves activity card
- Activity Feed: Enhanced empty state with Add Asset CTA
- Reports: Guidance cards explaining what each section shows when empty
- Onboarding: Welcome overlay for first-time users (localStorage flag)
- CSS: empty-state-card, guidance-card, esc-* classes, onboard-overlay