design: two-color palette — rename all tokens to --cream / --blue

Replace ochre-clay, carbon-black, burnt-oxide, slate-indigo with clean
two-color system: --cream (#f4f0e8) and --blue (#041cf3). Update every
component, utility class, and test assertion.

src/widgets/Navigation/ui/UtilityBar.tsx

@@ -15,11 +15,11 @@ export function UtilityBar() {
   }
 
   return (
-    <div className="fixed bottom-0 left-0 right-0 bg-ochre-clay brutal-border-top z-40">
+    <div className="fixed bottom-0 left-0 right-0 bg-cream brutal-border-top z-40">
       <div className="max-w-[2560px] mx-auto px-6 md:px-12 lg:px-16 py-4 flex items-center justify-between">
         <div className="flex items-center gap-4">
           <span className="text-sm uppercase tracking-wider">Contact</span>
-          <a href={`mailto:${CONTACT_LINKS.email}`} className="text-base hover:text-burnt-oxide transition-colors">
+          <a href={`mailto:${CONTACT_LINKS.email}`} className="text-base hover:opacity-60 transition-opacity">
             {CONTACT_LINKS.email}
           </a>
         </div>