remove manual update prompt UI and enable automatic silent service worker updates

frontend/src/components/ui/UpdatePrompt.tsx

@@ -1,6 +1,5 @@
+import { useEffect } from 'react';
 import { useRegisterSW } from 'virtual:pwa-register/react';
-import { RefreshCw } from 'lucide-react';
-import { Button } from './Button';
 
 // Check for SW updates every hour and on tab focus/visibility change
 const UPDATE_INTERVAL_MS = 60 * 60 * 1000;
@@ -33,23 +32,12 @@ export function UpdatePrompt() {
     },
   });
 
-  if (!needRefresh) return null;
-
-  return (
-    <div className="fixed top-0 inset-x-0 z-[60] bg-[#1B263B] text-white shadow-lg">
-      <div className="max-w-7xl mx-auto px-4 py-2 flex items-center justify-between gap-3">
-        <div className="flex items-center gap-2 text-sm">
-          <RefreshCw size={16} className="shrink-0" />
-          <span>Доступна новая версия приложения</span>
-        </div>
-        <Button
-          size="sm"
-          onClick={() => updateServiceWorker(true)}
-          className="bg-white text-[#1B263B] hover:bg-white/90"
-        >
-          Обновить
-        </Button>
-      </div>
-    </div>
-  );
+  useEffect(() => {
+    if (needRefresh) {
+      console.log('[PWA] New version detected, auto-updating...');
+      updateServiceWorker(true);
+    }
+  }, [needRefresh, updateServiceWorker]);
+
+  return null;
 }