Add environment variable CELERY_BEAT_SCHEDULE_FILENAME to support read-only rootfs environments

[potix2]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

When running Dify on AWS EKS, the container root filesystem is read-only. Celery Beat tries to write its schedule file to the default path and fails with a PermissionError. By allowing the schedule file path to be customized, Celery Beat can run normally in these environments.

2. Additional context or comments

I have tested the custom schedule file path on AWS EKS using /tmp/celerybeat-schedule.db, and Celery Beat works correctly. This change would make Dify more compatible with read-only rootfs environments.

3. Can you help us with this feature?

• [x] I am interested in contributing to this feature.

[dosubot[bot]]

Hi, @potix2. I'm Dosu, and I'm helping the Dify team manage their backlog and am marking this issue as stale.

Issue Summary:

• You requested adding a CELERY_BEAT_SCHEDULE_FILENAME environment variable to customize the Celery Beat schedule file path.
• This change aims to support environments with read-only root filesystems, like AWS EKS.
• You have tested this modification successfully and offered to contribute the implementation.
• There has been no further activity or maintainer response on this issue.

Next Steps:

• Please let me know if this issue is still relevant with the latest version of Dify by commenting here to keep the discussion open.
• If I do not hear back within 15 days, this issue will be automatically closed.

Thank you for your understanding and contribution!