fix(dashboard): Multiple components use raw Tailwind colors outside design token system

[OneStepAt4time]

Bug

Several components beyond SessionTable/PipelineDetail also use raw Tailwind color classes:

Components affected:

• HomeStatusPanel.tsx — border-void-lighter, text-cyan-300
• MetricCards.tsx — border-void-lighter (2x)
• MetricsPanel.tsx — border-void-lighter (2x)
• SessionMobileCard.tsx — border-void-lighter, bg-void, text-cyan, focus:ring-cyan, bg-void-lighter
• PipelineStatusBadge.tsx — bg-cyan/10, text-cyan, border-cyan/30
• SessionPreviewCard.tsx — text-cyan-200
• AgentBadge.tsx — bg-cyan-500/15, text-cyan-400, border-cyan-500/25

Impact: These components break in light theme. The raw Tailwind colors (cyan, void) are not mapped to light-mode equivalents.

Acceptance criteria:

• Replace all raw Tailwind color references with CSS var equivalents
• Test all listed components in both dark and light themes

Labels: dashboard, bug

[OneStepAt4time]

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