feat: refresh header logo and product name to Whitepages Pro API

[lhagenWP]

Summary

Updates the header chrome and product naming on the API documentation site to reflect the Whitepages Pro API branding throughout.

What changed

Header logo (src/components/layout/navigation-title.tsx, public/pro_api_logo.svg)

• New public/pro_api_logo.svg — the Whitepages Pro API wordmark with the blue/purple gradient. Reads cleanly on both light and dark backgrounds, so the separate gray/white variants (public/whitepages_gray_icon.svg, public/whitepages_white_icon.svg) are no longer needed and are removed.
• NavigationTitle simplifies to a single <Image> rendering the new logo.

Header logo destination (src/lib/layout.shared.tsx)

• nav.url now points at https://www.whitepages.com/pro-api so clicking the logo takes users to the Pro API marketing page.

Click event (src/components/layout/whitepages-logo-link.tsx, …test.ts)

• Replaces the prior WPAPIDocsHomepageLinkClicked event with WPClickedHeaderSiteLink, property LinkType: "API" per the new analytics taxonomy.
• The test is updated to assert the new event shape.

Product name in copy (18 content / metadata files)

• "Whitepages API" → "Whitepages Pro API" everywhere the product is named.
• Covers MDX page bodies and descriptions under content/docs/, page titles + OG metadata in src/app/layout.tsx and src/app/og/[...slug]/route.tsx, and the llms.txt feed.
• No false positives — e.g. purchasing-api.mdx already said "Whitepages Pro API" and is unchanged.

Verification

• validate-wrap just validate — passes
• Local dev render — header shows the new gradient wordmark, clicking it navigates to /pro-api and fires WPClickedHeaderSiteLink { LinkType: "API" }.
• Copy spot-checked across getting-started, references, mcp, and changelog pages.

Test plan

• Visit any docs page in the local dev server.
• Header should show the new gradient Whitepages Pro API wordmark.
• Click the logo → navigates to https://www.whitepages.com/pro-api.
• DevTools / Amplitude inspector should record WPClickedHeaderSiteLink with LinkType: "API".
• Spot-check page copy on any of: getting-started, getting-trial-api-key, making-your-first-request, references/index — should read "Whitepages Pro API" throughout.