fix: update Traefik dashboard domain to proxy.pivoine.art

Changed access control rule from traefik.pivoine.art to proxy.pivoine.art
to match the actual Traefik dashboard hostname configured in arty.yml.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

net/authelia/configuration.yml

@@ -70,7 +70,7 @@ access_control:
         - "mailpit.pivoine.art"
         - "scrapy.pivoine.art"
         - "restic.pivoine.art"
-        - "traefik.pivoine.art"
+        - "proxy.pivoine.art"
       policy: one_factor
 
     # Development services