docs: refresh CLAUDE.md and README with current project state, drop dead legacy pages

Both docs still described a frontend/-subfolder Vite/react-router-dom
setup that never existed in this repo's history, and were missing the
yt-dlp probe gating, SEO landing pages, sitemap, and 4-locale i18n
shipped in recent commits. Also removes src/app/page.tsx and
src/app/status/[uuid]/page.tsx, superseded by the [locale]-based
routes and unreachable since the next-intl middleware redirects all
non-API traffic into [locale]/...

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/page.tsx

@@ -1,10 +0,0 @@
-import { SubmitForm } from '@/components/SubmitForm'
-
-export default function Home() {
-  return (
-    <main style={{ padding: '2rem' }}>
-      <h1>Ombrora</h1>
-      <SubmitForm />
-    </main>
-  )
-}

src/app/status/[uuid]/page.tsx

@@ -1,15 +0,0 @@
-import { StatusView } from '@/components/StatusView'
-
-export default async function StatusPage({
-  params,
-}: {
-  params: Promise<{ uuid: string }>
-}) {
-  const { uuid } = await params
-  return (
-    <main style={{ padding: '2rem' }}>
-      <h1>Statut du telechargement</h1>
-      <StatusView uuid={uuid} />
-    </main>
-  )
-}