fix(dashboard): PipelineDetailPage uses raw Tailwind classes instead of CSS variables

[OneStepAt4time]

Bug

PipelineDetailPage uses raw Tailwind utility classes that are not part of the design token system:

• border-void-lighter → should be var(--color-void-lighter) or var(--color-border)
• hover:border-l-cyan → should be a CSS var reference
• hover:text-cyan → should be var(--color-accent-cyan)

Files affected:

• dashboard/src/pages/PipelineDetailPage.tsx (lines 145, 146, 159, 170, 182)

Impact: Light theme breaks — these hardcoded dark-theme colors don't adapt when the user switches to light mode.

Acceptance criteria:

• All raw Tailwind color references replaced with CSS var equivalents
• Both dark and light themes render correctly
• No visual regression in dark mode

Labels: dashboard, bug, a11y/accessibility

[OneStepAt4time]

Closed by PR #4069 (batch CSS variable migration, merged).