Remove env_file references for Portainer compatibility

- Portainer provides environment variables through UI
- env_file references caused deployment failure when .env.docker not present
- Environment variables now come from Portainer Stack configuration

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -53,8 +53,6 @@ services:
       dockerfile: Dockerfile
     container_name: keepitgoing-web
     restart: unless-stopped
-    env_file:
-      - .env.docker
     environment:
       DJANGO_SETTINGS_MODULE: config.settings.selfhosted
       DATABASE_URL: mysql://${DB_USER:-keepitgoing}:${DB_PASSWORD}@mariadb:3306/${DB_NAME:-keepitgoing}
@@ -88,8 +86,6 @@ services:
       dockerfile: Dockerfile
     container_name: keepitgoing-celery-worker
     restart: unless-stopped
-    env_file:
-      - .env.docker
     environment:
       DJANGO_SETTINGS_MODULE: config.settings.selfhosted
       DATABASE_URL: mysql://${DB_USER:-keepitgoing}:${DB_PASSWORD}@mariadb:3306/${DB_NAME:-keepitgoing}
@@ -112,8 +108,6 @@ services:
       dockerfile: Dockerfile
     container_name: keepitgoing-celery-beat
     restart: unless-stopped
-    env_file:
-      - .env.docker
     environment:
       DJANGO_SETTINGS_MODULE: config.settings.selfhosted
       DATABASE_URL: mysql://${DB_USER:-keepitgoing}:${DB_PASSWORD}@mariadb:3306/${DB_NAME:-keepitgoing}