fix: add DATABASE_URL to docker-compose environment

The application container was missing the DATABASE_URL env var, causing
pg Pool to default to localhost:5432 instead of the votc-db container.
This caused all application submissions to fail with ECONNREFUSED.

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

docker-compose.yml

@@ -4,6 +4,7 @@ services:
     container_name: votc
     restart: unless-stopped
     environment:
+      - DATABASE_URL=postgresql://votc:${POSTGRES_PASSWORD}@votc-db:5432/votc
       - INFISICAL_CLIENT_ID=${INFISICAL_CLIENT_ID}
       - INFISICAL_CLIENT_SECRET=${INFISICAL_CLIENT_SECRET}
       - INFISICAL_PROJECT_SLUG=valley-commons