Closes #5418

Description

What’s Changed

1. Throttled the upload speed calculation to once every 100ms.
2. Fixed an issue where the UI displayed Infinity MB/s when uploading many small files very quickly.

Additional Information

Previously, calculateSpeed was being called too frequently, which caused unrealistic values (e.g., Infinity MB/s) when processing batches of very small files. By introducing a 100ms throttle and averaging recent speeds, the upload speed display is now more accurate and stable.

Update

• Added byteToKbyte helper using filesize partial for KB conversion
• Introduced speedText computed property to replace raw MB-only speed
• Speed is now displayed dynamically:
  • < 1 MB → shown in KB/s
  • ≥ 1 MB → shown in MB/s
• Prevents meaningless 0.00 MB/s display

Checklist

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• I am aware the project is currently in maintenance-only mode. See README
• I am aware that translations MUST be made through Transifex and that this PR is NOT a translation update
• I am making a PR against the master branch.
• I am sure File Browser can be successfully built. See builds and development.