Document HeartMuLa test routing and timing

experiments/heartmula-3b/compose.yaml

@@ -16,7 +16,9 @@ services:
       - /data/models/heartmula:/models:ro
       - /data/music/heartmula:/output
     ports:
-      - "7863:7860"
+      - "127.0.0.1:7863:7860"
+    networks:
+      - frontend
     deploy:
       resources:
         reservations:
@@ -30,3 +32,8 @@ services:
       timeout: 5s
       retries: 20
       start_period: 180s
+
+networks:
+  frontend:
+    external: true
+    name: mike-ai_frontend