/admin shows each joint's servo control registers in one read-only table #443

Part of #439.

Done:

• [ ] The admin page (src/admin-page.ts, served by src/admin-routes.ts) has a 'Servos' section that fetches /servo-params and shows one row per joint and one column per register, all text-escaped.
• [ ] A servo that did not answer shows its error in its row. While someone is driving, the 409 is shown as a sentence, not as a blank table.
• [ ] Owner only, like the rest of /admin. A test proves the section renders from a fixture and a non-owner gets 404.
• [ ] bun scripts/design-lint.ts is clean if any src/web file is touched, and bun --cwd Software/so101 test passes.