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/nginx.conf

@@ -8,7 +8,10 @@ server {
         try_files $uri $uri/ /index.html;
     }
 
-    location /api/ {
+    # WebSocket feed. Kept in its own block so the upgrade headers are only set
+    # here, and so the API token is injected server-side on the handshake (the
+    # browser cannot set headers on a WebSocket).
+    location /api/ws {
         proxy_pass http://backend:8000;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
@@ -16,6 +19,16 @@ server {
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_read_timeout 3600s;
+        proxy_send_timeout 3600s;
+        proxy_set_header ${API_TOKEN_HEADER} "${API_TOKEN}";
+    }
+
+    location /api/ {
+        proxy_pass http://backend:8000;
+        proxy_http_version 1.1;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_read_timeout 3600s;
         # Inject the optional API token server-side so the browser never sees it
         # and the WebUI keeps working without any client changes.
         proxy_set_header ${API_TOKEN_HEADER} "${API_TOKEN}";