Resolve best mirror when downloading from ModDB

[Tosox]

Task Description

As a user, I need the downloader to select the best available mirror when fetching files from ModDB so that downloads are fast and reliable. Currently, the implementation always picks the first mirror link on the download page without evaluating availability or performance.

Acceptance Criteria

• All available mirrors on the ModDB download page are collected
• The best mirror is selected based on a suitable heuristic
• Fallback to the next available mirror if the selected one fails

Additional Information

Relevant code: ModDbUrlSource.resolve()