Refactor hardcoded styles to use token constants

Replaces hardcoded breakpoint values in `VideoCard.js` and `tailwind.source.css` with token constants and valid CSS calculations. Updates the token linting script to enforce these rules by removing the previous allowlists for these files. This ensures that all UI elements are defined by the central styling system.

js/designSystem.js

@@ -6,6 +6,8 @@ const FALLBACK_CONTEXT = Object.freeze({
   isNew: () => true,
 });
 
+export const BREAKPOINT_LG = 1024;
+
 export function getDesignSystemMode() {
   return NEW_MODE;
 }