feat: separate About/Clients/Partners into /o-kompanii/ page, add IndexNow meta

- Create /[lang]/o-kompanii/ page with About, Clients, Partners sections
- Remove those sections from homepage (Hero + Services + FAQ remain)
- Update Header nav: "О нас" now links to /o-kompanii/ instead of /#about
- AboutSection: support standalone prop (h1 vs h2)
- Root layout: add indexnow-key meta tag (key from public/40c65b...txt)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/layout.tsx

@@ -11,6 +11,9 @@ const manrope = Manrope({
 
 export const metadata: Metadata = {
   metadataBase: new URL('https://sag24.ru'),
+  other: {
+    'indexnow-key': '40c65b722891b81d944f2c3fea6cab95',
+  },
 }
 
 export default function RootLayout({ children }: { children: React.ReactNode }) {