fix: Create bct-network instead of using external network

- Change from external bct-network to locally created network
- Fix docker-compose.astro.yml network definition
- Fix docker-compose.prod.yml network definition
- Prevents "undefined networks" error during deployment

Networks are now created automatically by Docker Compose
instead of requiring pre-existing external network.

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

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

docker-compose.astro.yml

@@ -44,6 +44,5 @@ services:
       - bct-network
 
 networks:
-  default:
-    external:
-      name: bct-network
+  bct-network:
+    driver: bridge