🐛 fix: add shared network configuration for Docker Compose services

- Add dance-lessons-coach-network to both compose files
- Ensure build-cache and postgres containers can communicate
- Fix container-to-container connectivity
- Maintain same network name for consistency

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

docker-compose.build.yml

@@ -13,4 +13,11 @@ services:
     environment:
       - GOPATH=/go
       - PATH=/go/bin:/usr/local/go/bin:/usr/local/bin:/usr/bin:/bin
-    restart: unless-stopped
+    networks:
+      - dance-lessons-coach-network
+    restart: unless-stopped
+
+networks:
+  dance-lessons-coach-network:
+    name: dance-lessons-coach-network
+    driver: bridge