feat(seo): add WebSite and Organization structured data to the homepage

[KevinVandy]

Context

The tanstack.com homepage currently emits no JSON-LD. Adding a small homepage-only graph would give Google explicit, consistent signals for the TanStack site name, organization identity, logo, and verified social profiles.

Google documentation:

• Site names and WebSite markup: https://developers.google.com/search/docs/appearance/site-names
• Organization markup: https://developers.google.com/search/docs/appearance/structured-data/organization

Proposed scope

Add one SSR-visible JSON-LD @graph to the canonical homepage containing:

• WebSite
  • Stable @id such as https://tanstack.com/#website
  • name: TanStack
  • url: https://tanstack.com/
  • alternateName only if there is a real, consistently used alternative
  • publisher referencing the Organization node
• Organization
  • Stable @id such as https://tanstack.com/#organization
  • name: TanStack
  • legalName when confirmed
  • url: https://tanstack.com/
  • A crawlable square logo asset with explicit URL and dimensions where supported
  • sameAs links for verified TanStack profiles such as GitHub, X, Bluesky, and YouTube

Do not add SearchAction solely for the retired sitelinks search-box feature.

Acceptance criteria

• Exactly one connected WebSite/Organization graph is emitted on the canonical homepage.
• The graph is present in the raw SSR response.
• Names and URLs match visible homepage branding, canonical tags, Open Graph metadata, and the production apex hostname.
• Every sameAs URL is verified and owned by TanStack.
• The logo URL is indexable, stable, and suitable for Google organization markup.
• Duplicate HTTP or www homepage variants, if reachable during rollout, do not emit conflicting identity data.
• Tests verify schema shape and prevent duplicate WebSite or Organization nodes.
• The deployed homepage passes schema validation and Google Rich Results Test parsing.