Docs: deployment.md's UI paths lose their placeholders ("Admin → Users → → Deactivate"), because <user> and <account> render as HTML tags #624

Problem

Three web UI paths in docs/deployment.md write their placeholders as bare <user> and <account> in bold text, outside a code span:

• Deactivating users: (**Admin → Users → <user> → Deactivate**, …)
• Trusted-header authentication, the paragraph on publishing tokens: (**Admin → Users → <user> → Tokens**, or **Admin → Service accounts → <account>**)

Markdown reads them as raw HTML tags. GitHub's sanitizer drops the unknown tags, so the page reads "Admin → Users → → Deactivate" and "Admin → Service accounts → ." mdBook, which builds the docs site (cargo xtask docs, #623), drops them too and warns:

unclosed HTML tag `<user>` found in `deployment.md` while exiting Strong

Fix

Escape each placeholder with a backslash (\<user>, \<account>). GitHub and pulldown-cmark both render that as the literal text <user>. A code span would not fit, because the rest of the bold UI path is plain text.

CHANGELOG.md has the same problem in two 2.0.0 entries (<user>, <name>), but a change never edits it, so this issue covers docs/deployment.md only.