Unnecessary downloads when using S3 as storage

[hchengting]

Pre-submission Checklist

• I have searched the existing issues and this bug has not been reported yet
• I have tested this issue on the demo site or the latest version

Where did you encounter this bug?

Latest stable version (self-hosted)

Memos Version

v0.25.3

Bug Description

This is a follow-up to #5183.

When using S3 as storage, frontend requests for attachments are now handled by the memos instance downloading the attachment from S3 and then returning it to the frontend. This differs from the previous approach where the frontend directly downloaded attachments from S3.

This change results in unnecessary traffic consumption and workload.

Steps to Reproduce

1. Update memos to v0.25.3.
2. Open resource tab.
3. Slow loading speed due to unnecessary traffic consumption and workload.

Expected Behavior

No response

Screenshots & Additional Context

No response