feat: add e2b template

[phala-agent]

Summary

• Add the e2b prebuilt template with a CPU-safe Python SDK verifier
• Install/import real e2b==2.25.0 and e2b-code-interpreter==2.7.0 packages without creating sandboxes or requiring credentials
• Add upstream E2B icon and one templates/config.json entry routed to the Phala prebuilt template path

Validation

• python3 templates/validate.py
• docker compose -f templates/prebuilt/e2b/docker-compose.yml config >/tmp/e2b-compose-config.out
• git diff --check origin/main...HEAD
• Static audit: config id uniqueness, icon presence, no env_file, no host bind mounts, no Docker socket, no privileged mode, no GPU/device request, no secret defaults, no Sandbox.create(...)/run_code(...) verifier calls

Phala Cloud Smoke

• Deployed with phala deploy --profile hermes-admin-cvm-check --name auto-template-test-e2b-0529-1133 --compose templates/prebuilt/e2b/docker-compose.yml --instance-type tdx.small --node-id 12 --wait --no-public-logs --no-public-sysinfo --json
• CVM: cvm_zjdzb6Kv
• VM UUID: c8c581ff-5aa9-4b33-80d2-4a88fd780d79
• App ID: e38367091b2fe395822be88098b2881550f44d07
• Node: prod7 / node id 12
• phala ps reached dstack-app-1 running and healthy
• Endpoint probes passed:
  • GET /healthz -> HTTP 200, service=e2b-sdk-verifier, ok=true
  • GET /demo -> HTTP 200, sandbox_created=false, run_code_called=false, local Result formats text,json
  • GET /v1/models -> HTTP 200, model id e2b-local-sdk-verifier
• Cleanup verified: phala cvms delete cvm_zjdzb6Kv --force --json; follow-up get returned The requested CVM was not found

cc @Marvin-Cypher for review.

[phala-agent]

cc @Marvin-Cypher for review.

[Marvin-Cypher]

Reviewed template files, normalized tags, compose config, config validation, stale path cleanup, and compose safety scan. Checks are passing.