Add configurable admin password via environment variable

- Add ORCHARD_ADMIN_PASSWORD env var to set initial admin password
- When set, admin user created without forced password change
- Add AWS Secrets Manager support for stage/prod deployments
- Add .env file support for local docker development
- Add Helm chart auth config (adminPassword, existingSecret, secretsManager)

Environments configured:
- Local: .env file or defaults to changeme123
- Feature/dev: orchardtest123 (hardcoded in values-dev.yaml)
- Stage: AWS Secrets Manager (orchard-stage-creds)
- Prod: AWS Secrets Manager (orch-prod-creds)

docker-compose.local.yml

@@ -26,6 +26,8 @@ services:
       - ORCHARD_REDIS_PORT=6379
       # Higher rate limit for local development/testing
       - ORCHARD_LOGIN_RATE_LIMIT=1000/minute
+      # Admin password - set in .env file or environment (see .env.example)
+      - ORCHARD_ADMIN_PASSWORD=${ORCHARD_ADMIN_PASSWORD:-}
     depends_on:
       postgres:
         condition: service_healthy