Executed jobs inherit the backend's full environment, including every provider API key

[ldaiding]

        # Setup environment
        env = os.environ.copy()
        if env_vars:
            env.update(env_vars)

backend/app/code/run/job_runner.py:391

That environment is exactly where the provider secrets live: set_runtime_key writes them into the process env (backend/app/core/settings.py:209), and _load_runtime re-injects all persisted keys on boot (backend/app/core/settings.py:283).

Trigger: create a job with command: "env" and start it.
Observed: stdout.log contains OPENAI_API_KEY, ANTHROPIC_API_KEY, MOONSHOT_API_KEY, DATABASE_URL, … and that log is then registered as a downloadable artifact (backend/app/modules/code/code_jobs_api.py:185) and served by GET /{job_id}/logs/download (backend/app/modules/code/code_jobs_api.py:491). The secrets are now readable by anyone who can list jobs.
Expected: build the child environment from an explicit allowlist (PATH, HOME, LANG, PYTHONPATH) plus caller-supplied env_vars, never os.environ.copy().

This is a straightforward fix and it meaningfully reduces the blast radius of issue-09 even before sandboxing lands.