fix: PWA icon, robust socket.io reconnect, faster real-time sync

public/sw.js

@@ -30,6 +30,9 @@ self.addEventListener('fetch', (event) => {
   // Skip non-GET requests
   if (event.request.method !== 'GET') return
 
+  // Never intercept Socket.IO — let it pass through directly
+  if (pathname.startsWith('/socket.io')) return
+
   // Cacheable API routes: Network First with cache fallback (icons, hose-types, dictionary)
   if (CACHEABLE_API.some(p => pathname.startsWith(p))) {
     event.respondWith(