fix: set explicit network name to prevent compose prefix mismatch

Docker Compose prefixes network names with the project name by default.
The app container (started via docker run) was connecting to 'portfolio_dev'
while postgres/redis were on '<project>_portfolio_dev' - different networks.
Setting 'name: portfolio_dev' forces the exact name so all containers
share the same network.

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

docker-compose.dev.minimal.yml

@@ -36,6 +36,7 @@ services:
 
 networks:
   portfolio_dev:
+    name: portfolio_dev
     driver: bridge
 
 volumes: