fix(layout,splash): enforce global chrome across /lighthouse + overhaul first-visit splash logic

[devin-ai-integration]

Summary

Two related UX bugs, one PR.

1. Global layout chrome (incl. /lighthouse)

/lighthouse was rendering BrandHeader / BrandFooter / SiteContactDrawer / a bespoke CookieConsentBanner directly in its own layout.tsx, which meant it diverged from the rest of the marketing site (no sticky site-chrome-sticky wrapper, no mobile-nav overlay, a different cookie banner, different footer metadata surface, etc.).

• apps/web/src/app/lighthouse/layout.tsx is now a thin segment wrapper — metadata + fonts + LighthouseJsonLd + LighthouseTechFingerprints only.
• apps/web/src/app/lighthouse/page.tsx and apps/web/src/app/lighthouse/report/[id]/page.tsx wrap their content in the shared MarketingChrome, so lighthouse now gets the exact same sticky brand header (with the gold trim rule), mobile-nav overlay, reach-out dialog, site-body-canvas, BrandFooter, cookie consent banner, and GTM/analytics scripts as (site)/*.
• MarketingChrome gained four optional props so lighthouse can keep its "audit" chip in the header and its "Lighthouse Scanner v2 · Powered by Gemini / ElysiaJS / Next.js" attribution in the footer without forking the component:
  • headerCurrentSection?: "audit"
  • footerBuildTag?: string
  • footerPoweredBy?: ReadonlyArray<{ label; href }>
  • segmentClassName?: string
• /lighthouse/report/[id]/print is intentionally left outside MarketingChrome because the existing global @media print rules in layout-shell.css hide .site-body-canvas — keeping PDF output clean.

The gold trim (.dba-header-rule) lives inside BrandHeader and its CSS is already loaded globally via dba-global.css → brand-chrome.css, so consolidating every page onto MarketingChrome is what actually makes the trim render consistently everywhere.

2. First-visit splash popup (critical bug)

The splash was mounted inside HomePage (apps/web/src/components/marketing/HomePage.tsx), so it only existed in the React tree when the user rendered /. A visitor who landed on /lighthouse, /services/*, /contact, /tools, etc. as their first URL never saw the splash; it only fired on their second visit (when they navigated to /).

• FirstVisitSplash is now mounted once in the root layout (apps/web/src/app/layout.tsx), wrapped in a <Suspense fallback={null}> because useSearchParams forces the subtree onto the client.
• Removed the stale <FirstVisitSplash /> render from HomePage.
• Splash gating logic rewritten:
  • Bumped storage key dba_first_visit_shown_v1 → dba_first_visit_shown_v2 so existing visitors get evaluated once under the new rules.
  • localStorage access is wrapped in try/catch for private-mode / storage-disabled browsers.
  • Entry is classified as micro-saas (and the splash is skipped + marked shown) when:
    • pathname === "/tools" or pathname.startsWith("/tools/"), or
    • any of ref, source, utm_source, utm_campaign, utm_medium, utm_content search-param values match /micro[-_ ]?saas|microsaas/i.
  • All other first-time entries (from any URL) see the splash once, after a 1.5s delay.
  • The effect runs only on mount — deliberately not re-firing on client-side navigation (documented with a scoped biome-ignore for useExhaustiveDependencies).

Review & Testing Checklist for Human

• Hit each of these first, in a fresh incognito window (localStorage cleared) and confirm splash fires once ~1.5s after load and stays dismissed on further navigation: /, /lighthouse, /contact, /services/local-seo, an arbitrary marketing slug like /services/custom-web-design.
• Hit /tools first in a fresh incognito window → splash must not appear; then navigate to / → splash must still not appear (micro-saas entry sticks for that visitor).
• Hit /?utm_campaign=microsaas_launch first in a fresh incognito window → splash must not appear.
• Compare the /lighthouse page side-by-side with / and /tools: same sticky header, same gold trim under the header, same footer, same reach-out sticky button, same cookie consent banner. The only intentional differences are the "audit" chip in the header and the "Powered by Gemini / ElysiaJS / Next.js" row in the footer.
• Open a magic-link report URL /lighthouse/report/<id> — same chrome as above should render around the report, and the "Print / Save as PDF" CTA should still land on a clean /print page with no marketing chrome.

Notes

• The only CI lint diagnostic remaining is a pre-existing biome formatter warning on apps/web/src/components/JsonLd.tsx that is unrelated to this PR (confirmed by running bun run lint on main before any of these changes).
• bun run typecheck and bun run build both pass locally against this branch.

Link to Devin session: https://app.devin.ai/sessions/eb3d9c0a8a374727b60829b239ae5835
Requested by: @Designed-By-Anthony

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