fix(dashboard): render OnboardingTour for first-time users

[nyxsky404]

Summary

OnboardingTour was a fully-implemented component (driver.js guided tour, seen_onboarding PATCH, Supabase migration) that was never imported or rendered anywhere in the app, making the entire onboarding feature silently unreachable. This PR wires it up with a minimal, safe integration.

Closes #2302

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

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What Changed

• src/components/DashboardHeader.tsx
  • Imported OnboardingTour
  • Added seenOnboarding state (defaults to true — safe fallback so tour does not flash for returning users if the settings fetch is slow or fails)
  • Read seen_onboarding from the existing /api/user/settings response alongside is_public — no extra network request
  • Rendered <OnboardingTour /> conditionally when seenOnboarding === false

No changes to OnboardingTour.tsx itself — the markTourSeen() PATCH on dismiss was already correct.

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How to Test

1. Create a new DevTrack account (or manually set seen_onboarding = false in the users table for your account).
2. Visit /dashboard.
3. After ~800 ms the driver.js guided tour should launch, walking through the dashboard widgets.
4. Dismiss or complete the tour.
5. Refresh the page — the tour should not reappear (confirmed by seen_onboarding being set to true in the DB after step 4).

Expected result: New users see the onboarding tour exactly once. Returning users see nothing.

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Checklist

• Linked the related issue above
• Self-reviewed my own diff
• No unnecessary console.log, debug code, or commented-out blocks
• No TypeScript errors introduced (pnpm run type-check — errors shown are all pre-existing)
• No new tests required — the change is a conditional render wired to an existing API field
• No additional API calls added — reuses the existing /api/user/settings fetch already present in DashboardHeader

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Additional Context

seenOnboarding defaults to true intentionally. This ensures that if the settings API is slow, errored, or the field is null/undefined, the tour does not fire unexpectedly for returning users. It will correctly flip to false only when the API explicitly returns seen_onboarding: false (i.e., a genuinely new user).

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[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

Quality (optional):

• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

Validation (required to score):

• gssoc:approved — counts for points
• gssoc:invalid / gssoc:spam / gssoc:ai-slop — does not score

Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[nyxsky404]

The CI failures on this PR (Playwright smoke tests and Playwright visual regression) are pre-existing broken tests on main — they are not caused by the changes in this PR.

Root causes fixed:

• e2e/streak.spec.ts — duplicate aria-label on streak card div and tooltip button caused a strict-mode locator violation
• Visual regression — test heading selector @playwright-user's profile never matched the actual h1 (@playwright-user)
• landing-page-dark.png snapshot was accidentally zeroed in a prior merged commit
• Public profile test — no Supabase mock for server-side profile fetch in CI, so the page returned 404

Fixes have been applied to this branch. CI is Green.

[Priyanshu-byte-coder]

This PR has merge conflicts with the current main branch. Please rebase or merge main into your branch to resolve the conflicts, then push the updated branch. Once conflicts are resolved, this PR will be merged.

git fetch origin main
git merge origin/main
# resolve conflicts
git push