fix: Add REDIS_PASSWORD_FILE Docker Secret to staging-app service

- Add REDIS_PASSWORD_FILE=/run/secrets/redis_password to staging-app environment
- Add redis_password to staging-app secrets list
- Ensures REDIS_PASSWORD can be resolved from Docker Secret via *_FILE pattern
- Fixes issue where REDIS_PASSWORD was empty in staging-app even though secret exists

docker-compose.staging.yml

@@ -49,6 +49,7 @@ services:
       - QUEUE_CONNECTION=default
       # Use Docker Secrets via *_FILE pattern (Framework supports this automatically)
       - DB_PASSWORD_FILE=/run/secrets/db_user_password
+      - REDIS_PASSWORD_FILE=/run/secrets/redis_password
       - APP_KEY_FILE=/run/secrets/app_key
       - VAULT_ENCRYPTION_KEY_FILE=/run/secrets/vault_encryption_key
       - GIT_TOKEN_FILE=/run/secrets/git_token
@@ -60,6 +61,7 @@ services:
       - /etc/localtime:/etc/localtime:ro
     secrets:
       - db_user_password
+      - redis_password
       - app_key
       - vault_encryption_key
       - git_token