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.

app/page.tsx

@@ -1,38 +0,0 @@
-import type { SectionRecord } from '$entities/Section';
-import { getCollection } from '$shared/api';
-import type { NavItem } from '$widgets/Navigation';
-import { MobileNav, SidebarNav } from '$widgets/Navigation';
-import { SectionFactory } from '$widgets/SectionFactory';
-import { SectionsAccordion } from '$widgets/SectionsAccordion';
-
-/**
- * Portfolio home page.
- *
- * Fetches all sections at build time (SSG). Renders a fixed sidebar with
- * section navigation and a scrollable main column with accordion sections.
- */
-export default async function Home() {
-  const { items: sections } = await getCollection<SectionRecord>('sections', {
-    sort: 'order',
-  });
-
-  const navItems: NavItem[] = sections.map((s) => ({
-    id: s.slug,
-    label: s.title,
-    number: s.number,
-  }));
-
-  return (
-    <div className="min-h-screen lg:flex">
-      <SidebarNav items={navItems} />
-      <main className="flex-1 lg:ml-[33.333%] px-8 py-12 lg:py-16 lg:px-16">
-        <MobileNav items={navItems} />
-        <SectionsAccordion sections={sections}>
-          {sections.map((s) => (
-            <SectionFactory key={s.slug} slug={s.slug} />
-          ))}
-        </SectionsAccordion>
-      </main>
-    </div>
-  );
-}