feat: add litellm template

[phala-agent]

Summary

• Add the litellm prebuilt template for the upstream BerriAI/litellm repository.
• Run the official LiteLLM Proxy image in CPU-safe smoke mode with an empty model_list, no provider credentials, no GPU, no model downloads, and no database requirement.
• Add upstream-sourced icon templates/icons/litellm.jpg from ui/litellm-dashboard/public/assets/logos/litellm_logo.jpg.

Template files

• templates/prebuilt/litellm/docker-compose.yml
• templates/prebuilt/litellm/README.md
• templates/icons/litellm.jpg
• templates/config.json

Environment variables

• LITELLM_IMAGE_TAG (optional, default main-stable)
• LITELLM_LOG (optional, default INFO)
• LITELLM_MASTER_KEY (optional placeholder; set a strong value before exposing real model routes)
• OPENAI_API_KEY (optional placeholder for user-added model routes)
• ANTHROPIC_API_KEY (optional placeholder for user-added model routes)
• GOOGLE_API_KEY (optional placeholder for user-added model routes)

No real secrets are included.

Validation

• python3 templates/validate.py ✅
• git diff --check origin/main...HEAD ✅
• docker compose -f templates/prebuilt/litellm/docker-compose.yml config >/dev/null ✅
• Static audit ✅: README coverage, unique config ID, icon file present, correct Phala prebuilt repo route, no env_file, no host bind mounts, no privileged/host networking, no literal secret patterns.

Phala Cloud deployment smoke

• Profile/workspace: hermes-admin-cvm-check / h4x's projects
• Deploy command used tdx.small, --wait, --no-public-logs, and --no-public-sysinfo.
• Smoke CVM: fb7f8f74-eb9f-455f-9794-4b976469d916
• App ID: 3eab5fdf4c5df64bcdfad72da59098df3d8a9a45
• phala ps showed /dstack-litellm-1 running and healthy.
• Endpoint probes:
  • GET /health/liveliness -> HTTP 200, body "I'm alive!"
  • GET /health/readiness -> HTTP 200, body includes "status":"healthy"
  • GET /v1/models -> HTTP 200, body {"data":[],"object":"list"}

Cleanup

• Temporary CVM delete command returned success.
• Follow-up lookup returned The requested CVM was not found, so cleanup is verified.

cc @Marvin-Cypher for review.

[phala-agent]

cc @Marvin-Cypher for review.