fix: add strip-prefix back for server-ui asset serving

Nginx needs to see /assets/... not /server/assets/... to find the files.
Strip-prefix + BASE_PATH=/server now works correctly with the fixed image.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -203,6 +203,8 @@ services:
       - traefik.http.routers.server-ui.rule=PathPrefix(`/server`)
       - traefik.http.routers.server-ui.entrypoints=websecure
       - traefik.http.routers.server-ui.tls=true
+      - traefik.http.routers.server-ui.middlewares=server-ui-strip
+      - traefik.http.middlewares.server-ui-strip.stripprefix.prefixes=/server
       - traefik.http.routers.server-ui.service=server-ui
       - traefik.http.services.server-ui.loadbalancer.server.port=80
     networks: