feat(mechanic): update search placeholder to госномер only

Backend search now matches only on plate, so reflect that in the input
placeholder instead of misleading 'Поиск по номеру или VIN'.

Co-Authored-By: claude-flow <ruv@ruv.net>

mechanic-pwa/frontend/src/pages/Home.tsx

@@ -73,7 +73,7 @@ export default function Home() {
 
       <main className="p-4">
         <Input
-          placeholder="Поиск по номеру или VIN"
+          placeholder="Поиск по госномеру"
           value={q}
           onChange={(e) => setQ(e.target.value)}
           className="mb-4"