Add how-to page for the new SFTP SSH key management feature

Documents the customer-facing SFTP SSH Keys page shipped in WHP 2026.09.11
(sidebar: Security → SFTP SSH Keys) — adding/removing SSH public keys that
authorize SFTP login alongside the account password, useful for teams
sharing one hosting account without sharing a password. Walked the live
page as the demo customer account and captured real redacted screenshots
(empty state, filled Add Key form, populated key list). Also documents a
non-obvious live-verified detail: the visible Comment column reflects the
key's own comment (ssh-keygen -C), not the separate Note field, which only
goes to the audit log. Cross-linked from Create a site.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/content/docs/whp/how-to/create-a-site.mdx

@@ -56,6 +56,8 @@ When you connect via SFTP, your account home (`/docker/users/<your-user>/`) show
 
 Upload your files to the right place and the site picks them up immediately.
 
+Logging in with your account password works out of the box. If you'd rather use an SSH key instead — or need to let a teammate connect without sharing your password — see [Manage SFTP SSH keys](/whp/how-to/manage-sftp-ssh-keys/).
+
 ## Connect to databases and caches
 
 <Hostnames />
@@ -82,6 +84,7 @@ Open your domain in a browser. You should see your site, or the default "no cont
 
 - [Add a domain](/whp/how-to/add-a-domain/)
 - [Service hostnames](/whp/reference/service-hostnames/)
+- [Manage SFTP SSH keys](/whp/how-to/manage-sftp-ssh-keys/)
 
 ## Still stuck?