chore(deps): clear Gatsby 2 transitive npm deprecation warnings

Summary

Most remaining install deprecations come from the Gatsby 2 / webpack 4 stack (gatsby@2.32.13 and plugins), not from app source. Examples:

• urix / resolve-url (webpack4 → micromatch → snapdragon → source-map-resolve)
• eslint-loader@2.2.1
• @hapi/joi@15 and related @hapi/* (gatsby + workbox via gatsby-plugin-offline)
• chokidar@2.1.8 (webpack-dev-server@3)
• old rimraf / glob@7 / core-js@2 / debug@4.1.1 / uuid@3 under Gatsby tooling
• older npmlog via sharp under gatsby-plugin-manifest

Leaf-level overrides will not sustainably clear this set.

Parent inventory: #445 (Cluster B).

Recommended paths (in order of preference)

1. Long-term: complete #415 (Gatsby → Next.js) — removes the entire cluster.
2. Medium-term: coordinated Gatsby major upgrade (see open/blocked PRs #421, #413, #432, #444) with matching plugin majors.
3. Avoid: one-off overrides for every deprecated leaf package.

Acceptance criteria

• Choose path 1 or 2 and link the implementing PR(s)
• After landing, Cluster B warnings from #445 are gone on a clean install
• Build/test CI remains green on Node 18

Related

• #415 Migrate site from Gatsby to Next.js
• #446 Remove unused gatsby-image (quick win, independent)
• #445 Inventory of npm deprecation warnings

Start with parent inventory #445, then review #415 and the open or blocked upgrade PRs #421, #413, #432, and #444 to choose the Gatsby-to-Next.js migration or coordinated Gatsby upgrade. Done means the selected implementing PR(s) are linked, Cluster B warnings disappear on a clean install, and build/test CI stays green on Node 18.