feat(web): add HTTP proxy support via environment variables (#913)

[huboqiang]

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Related Issue

Closes #913

Description

In environments that require HTTP/HTTPS proxy access (e.g., corporate networks or restricted regions), Kimi CLI previously could not
connect to the API because aiohttp.ClientSession was created without proxy configuration.

This PR adds support for standard proxy environment variables, allowing users to configure proxy settings without modifying code or
configuration files:

• Automatic proxy detection: Reads HTTPS_PROXY/https_proxy/HTTP_PROXY/http_proxy environment variables
• Priority-based selection: HTTPS_PROXY > https_proxy > HTTP_PROXY > http_proxy, ensuring the most specific setting takes precedence
• Backward compatible: When no proxy variables are set, behavior remains unchanged

Changes

• src/kimi_cli/utils/aiohttp.py: Added proxy environment variable detection and proxy parameter to ClientSession
• tests/utils/test_aiohttp.py: Added 8 test cases covering no-proxy, 4 env var variants, 2 priority scenarios, and SSL connector
  configuration
• CHANGELOG.md: Added entry for HTTP proxy support
• docs/en/configuration/env-vars.md: Added Network proxy section with usage examples
• docs/zh/configuration/env-vars.md: Added 网络代理章节（中文翻译）
• docs/en/release-notes/changelog.md: Synced changelog update
• docs/zh/release-notes/changelog.md: Synced changelog update (中文翻译)

Checklist

• I have read the CONTRIBUTING document.

• I have linked the related issue, if any.

• I have added tests that prove my fix is effective or that my feature works.

• I have run make gen-changelog to update the changelog.

• I have run make gen-docs to update the user documentation.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.

[CyCle1024]

@RealKai42 Several developers have tried to "enable env http_proxy & socks_proxy feature" including this PR: #1479, #1465, #1236 (mine). It's really a problem for the users in enterprise with proxy-based internet access. Please take a look at the PR, thanks a lot.

[wangzhanxd]

I really need the proxy configuration feature. The company's servers are on the internal network and need to go through a proxy server to access external resources.

[wangzhanxd]

I need the proxy configuration feature badly @RealKai42

[CyCle1024]

I really need the proxy configuration feature. The company's servers are on the internal network and need to go through a proxy server to access external resources.

@wangzhanxd I think only the oauth is blocked due to missing trust_env=True. Normal llm api request is transferred by library kosong which use httpx as request api. httpx respects enviroment proxy variable by default. So you just need to bypass the oauth request and than using it normally. Nothing needs to be done when you upgrade latest kimi-cli, once you login on a device.