fix(dashboard): SessionTable + VirtualizedSessionList use ~30 raw Tailwind color classes

[OneStepAt4time]

Bug

SessionTable.tsx and VirtualizedSessionList.tsx have the highest concentration of raw Tailwind color classes in the dashboard:

• border-void-lighter (9 occurrences)
• bg-void (6 occurrences)
• text-cyan, border-cyan, hover:border-cyan, focus:border-cyan (8 occurrences)
• bg-cyan/10, bg-cyan/5, bg-cyan-900/30 (3 occurrences)
• bg-void-lighter (2 occurrences)

Files affected:

• dashboard/src/components/overview/SessionTable.tsx (~30 raw references)
• dashboard/src/components/overview/VirtualizedSessionList.tsx (~10 raw references)

Impact: Session table looks broken in light theme. Focus states, hover states, and selected state colors are all hardcoded to dark-theme values.

Acceptance criteria:

• Replace all raw Tailwind color references with CSS var equivalents
• Test session table in both dark and light themes
• Test focus/hover/selected states work correctly

Labels: dashboard, bug

[OneStepAt4time]

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