chore(deps): remove unused gatsby-image dependency

[jimmyandrade]

Summary

npm warn deprecated gatsby-image@2.11.0 appears on install. The package is a direct dependency in package.json (gatsby-image@2.11.0) but is not imported anywhere under src/ (no gatsby-image, GatsbyImage, or StaticImage usage).

Upstream guidance: migrate to gatsby-plugin-image — but for this repo the simplest fix is to remove the unused dependency.

Parent inventory: #445 (Cluster B quick win).

Acceptance criteria

• Remove gatsby-image from package.json / lockfile
• Confirm no remaining imports or GraphQL fragments that require it
• npm install --legacy-peer-deps no longer warns about gatsby-image
• Existing Jest suite stays green

Notes

If image components are reintroduced later under Gatsby, use gatsby-plugin-image (or Next.js Image after #415).