[threat-actors] Add GTG-2002 and GTG-5004

[nicolaiprodromov]

Adds two threat actors from Anthropic's August 2025 Threat Intelligence Report that were not yet in the galaxy:

• GTG-2002 – cybercriminal actor that used Claude Code for a scaled data-theft and extortion operation against at least 17 organizations. No country provided by the report.
• GTG-5004 – UK-based actor selling Claude-built ransomware as a service on dark web forums since January 2025 (GB).

Source: https://www-cdn.anthropic.com/b2a76c6f6992465c09a6f2fce282f6c0cea8c200.pdf