[Story-783] feat(tokens): migrate app UI to universal token space

sequenceDiagram
  autonumber
  participant design as Design Tokens
  participant css as Canonical CSS
  participant src as App Source
  participant audit as Audit & Tests
  design->>css: publish tokens spec
  css->>css: add ramp + aliases
  css->>src: import canonical
  src->>src: swap hex → var()
  src->>audit: regex sweep
  audit-->>src: tests assert vars