Never hang on "connecting": time out the socket and fall back

iOS Safari can leave a blocked wss:// upgrade hanging without firing
onclose/onerror, so the badge sat on "connecting". The socket now times out a
slow handshake after 5s, reports at most one failure per attempt, and the app
commits to polling after a 6s grace period if the socket never opens.

frontend/src/api.js

@@ -45,23 +45,47 @@ export function openSocket({ onMessage, onOpen, onClose, onError }) {
 
   const connect = () => {
     if (closed) return
+    let opened = false
+    let reported = false
     socket = new WebSocket(url)
+
+    // Report at most one failure per attempt (Safari often fires error *and*
+    // close for the same bad handshake).
+    const reportFailure = (code, detail) => {
+      if (reported) return
+      reported = true
+      onError?.(code, detail)
+    }
+
+    // Some mobile browsers leave a blocked upgrade hanging without firing
+    // onclose/onerror. Treat a slow handshake as a failure so the caller can
+    // fall back to polling instead of waiting forever.
+    const openTimeout = setTimeout(() => {
+      if (!opened) {
+        reportFailure(0, 'handshake timed out')
+        socket.close()
+      }
+    }, 5000)
+
     socket.onopen = () => {
+      opened = true
+      clearTimeout(openTimeout)
       attempt = 0
       onOpen?.()
     }
     socket.onmessage = (event) => onMessage?.(JSON.parse(event.data))
     socket.onclose = (event) => {
+      clearTimeout(openTimeout)
       onClose?.()
-      // 1008 = policy violation (token rejected); 1006 = abnormal close, which
-      // is what an auth/proxy rejection looks like to the browser.
-      onError?.(event.code, event.reason)
+      if (!opened) {
+        // 1008 = policy violation (token rejected); 1006 = abnormal close.
+        reportFailure(event.code, event.reason)
+      }
       schedule()
     }
     socket.onerror = (event) => {
-      // The browser hides details here; surface what it does give us.
-      const detail = event?.message || 'connection error'
-      onError?.(0, detail)
+      clearTimeout(openTimeout)
+      if (!opened) reportFailure(0, event?.message || 'connection error')
       socket.close()
     }
   }