[FEATURE]: Allow for Custom Server URL on hosted web

[OpeOginni]

Feature hasn't been suggested before.

• [x] I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

For istances where Opencode is served on further paths https://domain.com/workspace/1, this url will be the entrance to the web app, but only the origin will be used as the server url https://domain.com.

A nice feature would be to allow setting of custom Server URL, automatically set bu the ?url= query and can be changed in the UI as well.

[github-actions[bot]]

This issue might be a duplicate of existing issues. Please check:

• #6063: Serve on custom port / remote server broken - This issue describes the exact problem where the frontend is hardcoded to send requests to localhost:4096, failing when using custom ports or remote servers. Your feature request would solve this issue.
• #5844: Bug: Web terminal fails when accessing via network IP instead of localhost - Similar issue where the web app doesn't properly handle custom hostnames/IPs. It mentions using a query parameter (?url=) as a workaround, which aligns with your feature request.
• #5692: [FEATURE]: attach feature for opencode web command - Related feature request for attaching servers to the web app, which could be complementary to or part of the same solution.

Feel free to ignore if your specific case is different!

[adamdotdevin]

This was shipped earlier this morning, you can now add additional servers and switch between them

[OpeOginni]

Seen, it looks great testing it out currently. Thank you!