Apply theme color tokens to Topics + Home

[AndreRobitaille]

Summary

Apply semantic color tokens to Topic-first surfaces (Topics index, Topic detail, Home).

Requirements

• Use existing theme tokens where possible.
• Preserve readability and accessibility in both light/dark modes.

Acceptance criteria

• Topic-first pages fully reflect semantic color system.

[AndreRobitaille]

Closing as already satisfied. All Topic-first pages (Topics index, Topic detail, Home) use the semantic color token system via var(--color-*) references. Only 2 hardcoded hex values remain in footer styling (lines 463, 483 in application.css), which are outside the scope of this issue.