[Question]: The official documentation's instructions for using self-built Docker images appear to be incorrect？

[liyubo-debug]

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Issue Body: I followed the tutorial to build a Docker image according to https://ragflow.io/docs/v0.17.0/build_docker_image. The example provided a method to use the self-built image, but after testing, I found that modifying the configuration file location might be incorrect. According to the tutorial's modification steps, I noticed that the running image is still infiniflow/ragflow:v0.17.0-slim. Resolution: Instead of modifying configuration files directly, the correct approach is to set the RAGFLOW_IMAGE variable in the .env file to specify the new-built image. After updating .env: RAGFLOW_IMAGE=infiniflow/ragflow:nightly-slim and restarting the container with docker-compose -f docker-compose.yml up -d --no-pull, the running image correctly updated to infiniflow/ragflow:nightly-slim. Question: Is this the intended method to override the default image version? The current documentation may need clarification on this environment variable.