fix(infra): frontend upstream port 8080 → 3080

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: ImTotem

infra/nginx/bcsd-api.conf

@@ -16,7 +16,7 @@ upstream n8n {
 }
 
 upstream frontend {
-    server 127.0.0.1:8080;
+    server 127.0.0.1:3080;
 }
 
 # --- HTTP: ACME + redirect ---