feat(dashboard): replace checklist with next-step card + unified list

Phase 2 Task 41 — Dashboard redesign.

Backend:
- Extend GET /users/onboarding-status with email_verified and shop_setup_done.
- tried_ai_assistant kept in payload for backward-compat during deploy.

Frontend:
- New NextStepCard: surfaces the highest-priority incomplete onboarding item
  with a primary CTA. Priority order: verify email > set up shop > run first
  FlowPilot session > connect PSA > invite teammate > pick a plan (gated on
  trial stage warning/urgent/expired). Returns null when all done OR
  onboarding_dismissed.
- New SetupChecklist: unified single list (no SOLO/TEAM bifurcation), drops
  the stale tried_ai_assistant / Script Builder item, surfaces "Pick a plan"
  when trial stage is warning or later.
- Mounted on QuickStartPage below the hero with a "Show all setup steps"
  toggle. The whole onboarding section auto-hides when there's nothing left
  to nudge on, so the dashboard goes back to clean once setup is done.
- Removed the orphaned OnboardingChecklist component (was defined but never
  mounted).
- New useOnboardingStatus hook so page + components share one fetch contract.

Tests:
- Backend: test_onboarding_status_includes_email_verified_and_shop_setup_done.
- Frontend (Vitest): 13 new tests across NextStepCard, SetupChecklist, and
  QuickStartPage covering priority ordering, dismissal, the SOLO/TEAM
  removal, the toggle reveal, and the trial-stage gate on Pick a plan.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/api/endpoints/onboarding.py

@@ -90,6 +90,10 @@ async def get_onboarding_status(
             )
             connected_psa = (psa_q.scalar() or 0) > 0
 
+    # New (Phase 2 — Task 41)
+    email_verified = current_user.email_verified_at is not None
+    shop_setup_done = (current_user.onboarding_step_completed or 0) >= 1
+
     return OnboardingStatus(
         created_flow=created_flow,
         ran_session=ran_session,
@@ -99,6 +103,8 @@ async def get_onboarding_status(
         connected_psa=connected_psa,
         is_team_user=is_team_user,
         dismissed=current_user.onboarding_dismissed,
+        email_verified=email_verified,
+        shop_setup_done=shop_setup_done,
     )