Serve /api/ws without Basic auth so the live feed connects

Browsers don't reliably replay Basic-auth credentials on a WebSocket upgrade,
so the dashboard's live feed was stuck on "reconnecting" (only the 5s REST
poll worked). Give /api/ws a higher-priority Traefik router that skips Basic
auth; the backend still requires API_TOKEN, which nginx injects on the
handshake. The deploy now fails closed unless CRYPTO_API_TOKEN is set.

Also: split the nginx /api/ws block so upgrade headers are only set there, and
add reconnect backoff (2s -> 30s) so a failing socket stops hammering.

frontend/src/api.js

@@ -25,17 +25,32 @@ export const deletePreset = (id) => http.delete(`/presets/${id}`).then((r) => r.
 
 export function openSocket({ onMessage, onOpen, onClose }) {
   const proto = window.location.protocol === 'https:' ? 'wss' : 'ws'
+  const url = `${proto}://${window.location.host}/api/ws`
   let socket
   let retryTimer
   let closed = false
+  let attempt = 0
+
+  const schedule = () => {
+    if (closed) return
+    // Back off from 2s up to 30s so a persistently failing socket (e.g. auth)
+    // does not hammer the server, while a brief blip still reconnects fast.
+    const delay = Math.min(2000 * 2 ** attempt, 30000)
+    attempt += 1
+    retryTimer = setTimeout(connect, delay)
+  }
 
   const connect = () => {
-    socket = new WebSocket(`${proto}://${window.location.host}/api/ws`)
-    socket.onopen = () => onOpen?.()
+    if (closed) return
+    socket = new WebSocket(url)
+    socket.onopen = () => {
+      attempt = 0
+      onOpen?.()
+    }
     socket.onmessage = (event) => onMessage?.(JSON.parse(event.data))
     socket.onclose = () => {
       onClose?.()
-      if (!closed) retryTimer = setTimeout(connect, 2000)
+      schedule()
     }
     socket.onerror = () => socket.close()
   }