Flyto2 Core: LLM/API keys leak to an attacker-controlled base_url

Flyto2 Core is an execution kernel for automation and AI-agent workflows. Prior to 2.26.6, llm.chat reads provider keys such as OPENAI_API_KEY and ANTHROPIC_API_KEY from the environment and sends them in the Authorization: Bearer header to caller-controlled base_url, allowing an attacker to receive the operator's key on a public host that passes the SSRF guard. This issue is fixed in version 2.26.6.