Change app listen port from 8080 to 4000.

Dockerfile

@@ -20,9 +20,9 @@ ENV APP_ROOT=/app \
     TEMPLATES_DIR=/app/web/templates \
     STATIC_DIR=/app/web/static \
     MYSQL_DUMP_PATH=/data/wg.sql \
-    APP_PORT=8080
-EXPOSE 8080
+    APP_PORT=4000
+EXPOSE 4000
 HEALTHCHECK --interval=30s --timeout=5s --start-period=40s --retries=3 \
-  CMD curl -fsS http://127.0.0.1:8080/healthz >/dev/null || exit 1
+  CMD curl -fsS http://127.0.0.1:4000/healthz >/dev/null || exit 1
 USER nobody
 CMD ["/app/wg-panel"]