fix: restore dark dashboard contrast

[PeterGuy326]

Summary

• isolate Ant Design light and dark CSS variable scopes so SSR light variables cannot override hydrated dark components
• explicitly map Ant text, controls, navigation, table, card, and breadcrumb states to the shared semantic palette
• improve dense metadata readability, accessible control boundaries, and table hover/link contrast without modifying upstream design-system root tokens
• extend the design contract with theme-scope and dark contrast checks

Validation

• dashboard typecheck and production build
• design contract and diff checks
• production dependency audit
• Compose configuration and live port 3001 smoke: health, readiness, overview with 3 queues, proxy isolation
• final contrast audit: no P0/P1; control borders >= 3:1 and table danger text >= 5.42:1 on hover