feat: add jcode template

[phala-agent]

Summary

• Add a Phala Cloud prebuilt template for 1jehuang/jcode.
• Upstream repository: https://github.com/1jehuang/jcode
• Template files: templates/prebuilt/jcode/docker-compose.yml, templates/prebuilt/jcode/README.md, templates/config.json
• Icon: jcode.png; source documented in the README.

Environment variables

• See the template README for optional provider/runtime environment variables. No real secrets are included.

Validation

• python sdks/templates/validate.py
• git -C sdks diff --check origin/main...HEAD
• docker compose -f sdks/templates/prebuilt/jcode/docker-compose.yml config >/dev/null
• static audit: README coverage, config ID uniqueness, icon file, forbidden compose directives, host bind mounts, and secret-like literals

Deployment smoke

• Deployed with phala deploy --profile hermes-admin-cvm-check --instance-type tdx.small --node-id 12 --wait --no-public-logs --no-public-sysinfo
• Smoke CVM: d44bdc91-26f8-4b38-a54a-33231774c015
• Smoke app: 17f7b2f59c20f45f033326434f317254376c336b
• Endpoint probe: https://17f7b2f59c20f45f033326434f317254376c336b-8080.dstack-pha-prod7.phala.network/healthz -> 200 2379 0.190846 rc=0
• Cleanup: temporary smoke CVM deletion requested and verified separately.

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.