feat: Support for HTTP proxy

[hiro-v]

Problem

• User request - Discussion
• Tried to use Jan in enterprise network with air-gapped environment. This network has firewall that blocks huggingface. However, they can only see the proxies settings but not able to change it (requires Windows Administrator password)

Success Criteria

• An extension that can be toggled on or off
• A json file in HOME/jan for proxies settings

Additional context Add any other context or screenshots about the feature request here.

[dan-menlo]

@vuonghoainam Great job writing a clear spec. I actually created an issue for this a couple of days ago (I will close the previous issue in favor of this issue, as you've written it very well)

https://github.com/janhq/jan/issues/1040

Great job!

[freelerobot]

Nit: removed direct references to name/pronouns/"customer" in issue description.

[markmehere]

Linking to #1512

[Van-QA]

tested and looking good via the testing on Jan v0.4.4-160 ✅