Remove temporary dependency overrides after upgrading Next.js

[jonathanhefner]

PR #25 added temporary pnpm overrides for transitive versions selected by Next.js 16.2.10:

• postcss versions below 8.5.10 are overridden to 8.5.22
• sharp versions below 0.35.0 are overridden to 0.35.3

Remove each override once a stable Next.js release permits or directly selects a patched version. The sharp upgrade has already landed upstream in vercel/next.js#95507 but was not yet included in the stable Next.js release available when PR #25 merged.

Completion criteria

• Upgrade Next.js to a stable release with compatible patched PostCSS and Sharp dependencies.
• Remove every override that is no longer necessary from package.json.
• Regenerate pnpm-lock.yaml with pnpm rather than editing it directly.
• Confirm pnpm why postcss sharp resolves supported, patched versions without the removed overrides.
• Confirm pnpm audit reports no vulnerabilities.
• Run the production build successfully.
• Verify the resulting Vercel preview deployment.

The overrides may be removed independently if upstream support arrives at different times.