Add logo.png and favicon.ico, update nav/footer/JSON-LD

src/components/Footer.jsx

@@ -9,7 +9,7 @@ export default function Footer() {
   return (
     <footer className="bg-slate-900 text-slate-400 py-10">
       <div className="max-w-6xl mx-auto px-4 sm:px-6 flex flex-col md:flex-row items-center justify-between gap-4">
-        <span className="text-white font-semibold">Сисадмингрупп</span>
+        <img src="/logo.png" alt="Сисадмингрупп" className="h-7 w-auto brightness-0 invert" />
         <span className="text-sm">{year} © {t('footer.rights')}</span>
         <div className="flex flex-wrap justify-center gap-x-6 gap-y-1 text-sm">
           {phones.map((p, i) => (