Render legal links as a bare Settings page footer

Summary

Terms, Privacy, and Security are currently presented inside a boxed section on Settings. They should instead appear as simple footer links at the bottom of the Settings page.

Acceptance criteria

• Remove the card or boxed treatment around the legal links on Settings.
• Render Terms, Privacy, and Security as compact bare links in the page footer.
• Preserve the existing destinations:
  • https://trackslash.com/terms
  • https://trackslash.com/privacy
  • https://trackslash.com/security
• Keep the links keyboard-accessible and readable in light and dark modes.
• Do not reintroduce these links in the application sidebar.
• Update Settings rendering tests to cover the footer placement and absence of the boxed treatment.