Fix sw.js: exclude /hubs/ and PollSession from SW interception

SW fetch() wraps SSE responses in a buffered Response, preventing SignalR
streaming — handshakes time out after 15s as a result. Exclude /hubs/ and
/Kiosk/PollSession so the browser handles them directly without SW wrapping.

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

src/PowderCoating.Web/wwwroot/sw.js

@@ -1,11 +1,26 @@
 // Minimal service worker — required for PWA installability.
-// No caching: all requests pass through to the network normally.
-// This exists solely so browsers recognize the site as installable,
-// which causes iOS/Android to persist camera permissions after "Add to Home Screen."
+// No caching: all requests pass through to the network.
+// Exists solely so browsers recognize the site as installable
+// (iOS/Android persist camera permissions after "Add to Home Screen").
+//
+// IMPORTANT: /hubs/ (SignalR) requests are excluded from interception entirely.
+// Service worker fetch() wraps SSE/WebSocket responses in a buffered Response,
+// which prevents real-time streaming — SignalR handshakes time out as a result.
+
+const SKIP_PREFIXES = ['/hubs/', '/Kiosk/PollSession'];
 
 self.addEventListener('install', () => self.skipWaiting());
 self.addEventListener('activate', e => e.waitUntil(self.clients.claim()));
+
 self.addEventListener('fetch', e => {
-    if (new URL(e.request.url).origin !== self.location.origin) return;
+    const url = new URL(e.request.url);
+
+    // Always skip cross-origin requests
+    if (url.origin !== self.location.origin) return;
+
+    // Skip SignalR hubs and kiosk polling — let the browser handle these directly
+    if (SKIP_PREFIXES.some(p => url.pathname.startsWith(p))) return;
+
+    // Passthrough: no caching, no modification
     e.respondWith(fetch(e.request));
 });