Fix: Return empty arrays instead of null for device JSON fields

[mogilevich]

Summary

• Fix frontend crash (TypeError: Cannot read properties of null (reading 'map')) on device control page caused by supported_stream_types and installed_apps being serialized as null instead of [] in JSON responses.
• Initialize InstalledApps with make([]string, 0) in GetInstalledAppsIOS and GetInstalledAppsAndroid so error paths return [] not null.
• Set SupportedStreamTypes based on device OS in provider's DeviceInfo handler (was never set on provider side).
• Initialize both array fields when creating hub device entries in GetLatestDBDevices.

Root cause

In Go, var s []string is nil, which serializes to JSON null. The frontend calls .map() on these fields, which crashes React when they are null.

[mogilevich]

How to reproduce

1. Open the device list at /devices
2. Click Use on any device (reproduced on iPhone XS, iOS 16.6)
3. The control page at /devices/control/:udid shows UI for ~1 second, then crashes to a blank screen (just background color)

Browser console

In Use WebSocket connection opened
TypeError: Cannot read properties of null (reading 'map')
    at J3 (main.60dea171.js:1:725196)

API response (/device/:udid/info)

{
  "supported_stream_types": null,
  "installed_apps": null
}

Both fields are null because:

• SupportedStreamTypes is never set on the provider side
• InstalledApps uses var s []string which is nil in Go → null in JSON

[gifflet]

I've reviewed the changes and left some comments inline with suggestions for improvement.

[gifflet]

@mogilevich, everything looks good now. @shamanec, any other considerations before approving?

[shamanec]

@mogilevich @gifflet supported_stream_types is never read on on the device control page, so I doubt this was part of the issue but other than that - lgtm

[gifflet]

Yeah, the supported_stream_types fix doesn’t apply to the control page, but it improves api consistency

[shamanec]

thanks for checking it out @gifflet , thank you for the contribution @mogilevich