feat(brand): adopt the schoolcompare identity across the site

Implements the supplied brand guideline: the pin-and-leaf mark, the lowercase
schoolcompare wordmark, Manrope for headings and Inter for everything a person
reads a number from, the deep-teal/coral/mustard/sage palette, and the rounder
geometry the guideline asks for.

The landing hero is rebuilt to the concept: a Sand panel carrying the
proposition, the search and a trust line, with the brand landscape bleeding to
the panel's right edge, followed by the four value props.

Concept vs reality — where the guideline describes something this product does
not have, the real feature takes its place and the decision is recorded in a
code comment next to it:

- The Thriving Score is not implemented. Four of its five sub-scores (pastoral,
  enrichment, community, facilities) have no source in DfE or Ofsted data, and
  its band names are Ofsted's own, which would sit beside the real Ofsted grade
  and be indistinguishable from it.
- Guides, About, Favourites and Sign in are not added to the nav — there are no
  such pages and no accounts system. Rankings and Admissions, which the
  guideline omits, keep their places because they exist.
- The fourth value prop is "Never miss a deadline" rather than "Save & revisit",
  which would need shortlisting.

Two deviations from the supplied swatches, both forced by contrast and both
confined to text and fills. Coral #F97360 under a white label measures 2.75:1
against a 4.5 floor, so --action is a darkened #BE3C27 and the original coral
survives as --coral for tints, borders and illustration. Mustard #F2C94C is
1.5:1 as text, so --mustard-ink carries labels while --mustard stays exact for
fills and rings. Every token clears AA on all three light grounds; Sand is the
binding one, so several values sit a step darker than white alone would need.

The guideline is light-only, but the site already ships a dark theme, so it is
rebuilt from the same tokens rather than dropped.

Verified: tsc clean, 159/159 unit tests, production build green, and the
generated share card and app icon render from the new mark. The hero and the
site chrome were rendered from the compiled CSS and the prerendered markup to
confirm Manrope and Inter actually resolve — a font token that silently falls
back has shipped here before.

nextjs-app/app/layout.tsx

@@ -1,5 +1,5 @@
 import type { Metadata, Viewport } from 'next';
-import { Schibsted_Grotesk, Literata } from 'next/font/google';
+import { Manrope, Inter } from 'next/font/google';
 import Script from 'next/script';
 import { Navigation } from '@/components/Navigation';
 import { Footer } from '@/components/Footer';
@@ -7,23 +7,22 @@ import { ComparisonToast } from '@/components/ComparisonToast';
 import { ComparisonProvider } from '@/context/ComparisonProvider';
 import './globals.css';
 
-// Schibsted Grotesk carries the whole interface — headings, labels, and every
-// figure. It was drawn for news brands, so its tabular numerals hold a column
-// properly, which matters on a page that is mostly percentages.
-const schibsted = Schibsted_Grotesk({
+// Manrope carries headings and key messaging — the guideline's "friendly,
+// modern personality". It never sets body copy or a control.
+const manrope = Manrope({
   subsets: ['latin'],
-  weight: ['400', '500', '600', '700'],
-  variable: '--font-schibsted',
+  weight: ['500', '600', '700'],
+  variable: '--font-manrope',
   display: 'swap',
 });
 
-// Literata is for prose only — the admissions guide, methodology notes, the
-// editorial sections. It never touches a number or a control.
-const literata = Literata({
+// Inter carries body copy, every control and every figure — chosen in the
+// guideline for clarity and legibility. Its tabular numerals hold a column
+// properly, which matters on a page that is mostly percentages.
+const inter = Inter({
   subsets: ['latin'],
-  weight: ['400', '600'],
-  style: ['normal', 'italic'],
-  variable: '--font-literata',
+  weight: ['400', '500', '600', '700'],
+  variable: '--font-inter',
   display: 'swap',
 });
 
@@ -36,8 +35,8 @@ export const viewport: Viewport = {
   // These must match --bg-primary in globals.css for each theme, or the
   // browser chrome and the page disagree at the top edge of the screen.
   themeColor: [
-    { media: '(prefers-color-scheme: light)', color: '#f2f1ed' },
-    { media: '(prefers-color-scheme: dark)', color: '#10151b' },
+    { media: '(prefers-color-scheme: light)', color: '#FAFAF8' },
+    { media: '(prefers-color-scheme: dark)', color: '#111A20' },
   ],
 };
 
@@ -87,7 +86,7 @@ export default function RootLayout({
     // at :root, so --font-display computed to the guaranteed-invalid value and
     // every font-family that referenced it silently fell back — the whole site
     // rendered in Times.
-    <html lang="en" className={`${schibsted.variable} ${literata.variable}`}>
+    <html lang="en" className={`${manrope.variable} ${inter.variable}`}>
       <head>
         <link rel="preconnect" href="https://analytics.schoolcompare.co.uk" />
         <link rel="preconnect" href="https://api.postcodes.io" />