fix: route all traffic through nginx; remove direct /api->backend ingress rule

Traefik forwards /api/auth/login to the backend verbatim, causing 404.
Nginx already strips the /api prefix correctly via proxy_pass with trailing
slash. Routing everything through frontend/nginx avoids the double-routing
and the need for a StripPrefix middleware.

helm/shorefront/templates/ingress.yaml

@@ -13,13 +13,6 @@ spec:
     - host: {{ .Values.ingress.host }}
       http:
         paths:
-          - path: /api
-            pathType: Prefix
-            backend:
-              service:
-                name: backend
-                port:
-                  number: 8000
           - path: /
             pathType: Prefix
             backend: