Update hardcoded HTTP User-Agent to a current browser signature

[Tosox]

Task Description

As a user, I need the HTTP client to send a current and accurate User-Agent header so that downloads are not blocked or throttled by CDNs. The current header identifies as Firefox 57 on Linux, which is outdated and inconsistent with the application running on Windows.

Acceptance Criteria

• The User-Agent string is updated to a current browser signature
• The User-Agent reflects a Windows platform to match the target environment

Additional Information

Relevant code: HttpClient.java line 12 where USER_AGENT is hardcoded

[Tosox]

Changes will be reverted, as ModDB blocks this User-Agent