feat: propagate NO_PROXY and configurable env vars into sandbox execution environment

[kurokobo]

Summary

Sandbox-injected environment variables (e.g. custom CA paths, NO_PROXY) were silently dropped at the boundary between the container process and the sandboxed Python/Node.js subprocess.

This PR fixes that by:

1. Forwarding NO_PROXY automatically alongside the existing proxy variables.
2. Fixing HTTP_PROXY/HTTPS_PROXY not being forwarded in the Node.js runner (bug parity with Python runner).
3. Adding allowed_env_vars — an administrator-controlled whitelist of environment variable names to forward from the container into the execution environment.

Closes #272

Configuration

# conf/config.yaml
proxy:
  no_proxy: 'localhost,127.0.0.1,.internal.example.com'
allowed_env_vars:
  - SSL_CERT_FILE
  - REQUESTS_CA_BUNDLE
  - CURL_CA_BUNDLE
  - NODE_EXTRA_CA_CERTS
  - AWS_CA_BUNDLE

Or via environment variables:

NO_PROXY=localhost,127.0.0.1
ALLOWED_ENV_VARS=SSL_CERT_FILE,REQUESTS_CA_BUNDLE,CURL_CA_BUNDLE,NODE_EXTRA_CA_CERTS,AWS_CA_BUNDLE

Tests

Container configuration:
Tested with following docker-compose.override.yaml:

services:
  sandbox:
    image: dify-sandbox:local   # ✅ Locally built image with this PR
    environment:
      NO_PROXY: localhost,127.0.0.1,.internal.example.com  # ✅ New env var
      ALLOWED_ENV_VARS: MY_CUSTOM_VAR,ANOTHER_VAR  # ✅ Propagate following to env vars to the script runtime
      MY_CUSTOM_VAR: hello_from_container
      ANOTHER_VAR: world
      UNLISTED_SECRET: this_should_not_be_exposed  # ✅ This should not be propagated

App:
In code blocks, I run code in both Python and JavaScript that simply prints the value of a specified environment variable.
If the environment variable does not exist, output UNDEFINED.

Result:

I can confirm:

• ✅ NO_PROXY is automatically propagated.
• ✅ MY_CUSTOM_VAR and ANOTHER_VAR are propagated by ALLOWED_ENV_VARS
• ✅ UNLISTED_SECRET is NOT propagated since it is not listed in ALLOWED_ENV_VARS

[kurokobo]

@crazywoola @wylswz @BeautyyuYanli
Just to clarify, I understand that the sandbox environment itself will likely be transitioning to dify-agentbox.

That said, the existing dify-sandbox is still very easy to use without any special setup, so I believe there is still sufficient demand for it. For that reason, I submitted this enhancement.

I’d appreciate it if you could consider merging it and releasing it. Thanks!