chore(deps): bump axios and postcss in website lockfile (#781)

## Summary
Resolves Dependabot alerts in `website/pnpm-lock.yaml` via a
lockfile-only update (`pnpm update -r --lockfile-only --depth Infinity
axios postcss serialize-javascript`):

- **axios** → 1.16.0 (closes alerts #116-#128)
- **postcss** → 8.5.14

## Not addressed here
- **serialize-javascript** — pinned at 6.0.2 by transitive parents;
patched version is 7.x, which is a major bump. Requires a
`pnpm.overrides` entry in `website/package.json` (or waiting for
upstream parents to bump).

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>