[Bug]: PWA Icon Doesn't Display When Using Reverse Proxy

### Is there an existing issue for this?

- [X] I have searched the existing issues

### OS/Web Information

- Web Browser: Safari
- Local OS: iPadOS 15.5
- Remote OS: Libreelec (Linux Server Docker)
- Remote Architecture: x86_64
- `code-server --version`: v4.4.0

### Steps to Reproduce

1. Reverse Proxy code-server
2. Open code-server via the proxied subdomain on an iPad using Safari
3. Tap the Share Button
4. Press Add to Home Screen

### Expected

The home screen icon should resemble the favicons in the favicon folder

### Actual

See the home screen icon which is a screenshot of the VS Code workbench (current page view)

### Logs

_No response_

### Screenshot/Video


### Does this issue happen in VS Code?

- [X] I cannot reproduce this in VS Code.

### Are you accessing code-server over HTTPS?

- [X] I am using HTTPS.

### Notes

Tried to add favicon routes using Nginx but that didn't work either.

Start by reproducing the Safari on iPadOS 15.5 flow through an HTTPS reverse-proxied code-server instance, then inspect how the PWA home-screen icon is selected versus the favicon folder. Done means adding code-server to the iPad home screen produces the expected favicon-style icon rather than a screenshot of the current workbench.

Written by the indexing model from the issue text.