Add real-time download speed indicator to the transfer box

[iManGaaX]

Summary

Introduces a real-time download speed calculation and display feature to the MTA transfer box UI. Players can now see their active resource and map download speeds formatted cleanly in MB/s, KB/s, or B/s alongside the progress percentages.

Motivation

Previously, the transfer box showed only downloaded and total sizes, leaving players without a clear indication of their actual download performance or whether a slow download had stalled. This enhancement provides immediate, transparent feedback on network throughput during asset transfers.

Test plan

1. Compiled the MTA client source code locally.
2. Connected to a test server with large resources or map assets to trigger the transfer box.
3. Verified that the download speed is dynamically calculated and displayed in the window title.
4. Confirmed that the speed properly scales between B/s, KB/s, and MB/s and remains stable.

Checklist

• Your code should follow the coding guidelines.
• Smaller pull requests are easier to review. If your pull request is beefy, your pull request should be reviewable commit-by-commit.

[Haxardous]

Thank you for the PR.

I believe it would be cleaner to exclude the "Speed:" prefix before the actual download speed, as it is self-explanatory.

[iManGaaX]

Thank you for the PR.

I believe it would be cleaner to exclude the "Speed:" prefix before the actual download speed, as it is self-explanatory.

Thanks. i have now removed the word “Speed:”