fix(ops): add missing env_file to celery-beat and quiet Stripe log spam

celery-beat was missing env_file and DATABASE_URL, so it had no access
to app config (Stripe keys, etc.). Also downgrade "Stripe API key not
configured" from warning to debug to stop log spam when Stripe is not
yet set up.

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

docker-compose.yml

@@ -102,9 +102,13 @@ services:
     profiles:
       - full  # Only start with: docker compose --profile full up -d
     command: celery -A app.core.celery_config beat --loglevel=info
+    env_file: .env
     environment:
+      DATABASE_URL: postgresql://orion_user:secure_password@db:5432/orion_db
       REDIS_URL: redis://redis:6379/0
     depends_on:
+      db:
+        condition: service_healthy
       redis:
         condition: service_healthy
     mem_limit: 128m