docs(data-security): add bun package manager example (#83735)
Adds the `bun add server-only` command to the data security guide.
This change adds the missing Bun package manager example to the
`docs/01-app/02-guides/data-security.mdx` file, ensuring consistency
with other documentation sections.
Fixes #83734
Co-authored-by: Joseph <joseph.chamochumbi@vercel.com>
