[Bug]: Mattermost tray icon missing on Ubuntu 26.04 in 6.3.0, shows in 6.2.2

Nobody has claimed this yet.

### Checks before filing an issue

- [x] This issue doesn't reproduce on web browsers (such as in Chrome). If it does, [issue reports go to the Mattermost Server repository](https://github.com/mattermost/mattermost-server/issues).
- [x] I have checked the [issue tracker](https://github.com/mattermost/desktop/issues) and have not found an issue that matches the one I'm filing. This should include closed issues.
- [x] This issue is not a troubleshooting question. Troubleshooting questions go here: https://forum.mattermost.com/c/trouble-shoot/16.
- [x] This issue is not a feature request. You can request features and make product suggestions here: https://mattermost.com/suggestions/.
- [x] This issue reproduces on the most recent [stable version](https://github.com/mattermost/desktop/releases/latest), or the most recent [prerelease version](https://github.com/mattermost/desktop/releases) of the Mattermost Desktop App.
- [x] I have read the [contribution guidelines](https://github.com/mattermost/desktop/blob/master/CONTRIBUTING.md).

### Mattermost Desktop Version

6.3.0 (snap)

### Operating System

Ubuntu 26.04, GNOME 50.1

### Mattermost Server Version

11.0.2

### Steps to reproduce

1. Install Mattermost Desktop 6.3.0 from Snap.
2. Launch Mattermost.
3. Observe that the Mattermost tray/status indicator is not displayed.
4. Revert the Snap to Mattermost Desktop 6.2.2.
5. Launch Mattermost again.

### Expected behavior

The Mattermost tray/status indicator should be displayed, as it was in version 6.2.2.

### Observed behavior

The tray/status indicator is missing in 6.3.0.

Reverting to 6.2.2 immediately restores the indicator under the same Ubuntu/GNOME environment.

Other applications' AppIndicators continue to work normally.

### Log Output

```shell
[2026-08-20 12:16:35.372] [error] Logger Log level set to: { level: 'info' }
[2026-08-20 12:16:35.559] [error] Logger Log level set to: { level: 'error' }
[2026-08-20 12:16:39.313] [error] [WebContentsEventM...] [bb7f7b05-c86c-4e9...] [015bceed-c460-489...] [renderer] Uncaught (in promise) Error: Invalid or missing user_id parameter in request URL.
[2026-08-20 12:38:43.971] [error] [App.App] "child-process-gone" The child process has crashed. Details: {
details: {
type: 'Utility',
reason: 'killed',
exitCode: 15,
serviceName: 'network.mojom.NetworkService',
name: 'Network Service'
}
}
[2026-08-20 12:38:58.145] [error] Logger Log level set to: { level: 'info' }
[2026-08-20 12:38:58.257] [error] Logger Log level set to: { level: 'error' }
[2026-08-20 12:38:58.962] [error] [App.Utils] clearAppCache { err: 'TypeError: Object has been destroyed' }
[2026-08-20 12:39:03.983] [error] [WebContentsEventM...] [d3e7c5af-0e04-4c3...] [3161dc53-41ca-4ea...] [renderer] Uncaught (in promise) Error: Invalid or missing user_id parameter in request URL.
```

### Additional Information

Self hosted server.
This appears to be a regression between Mattermost Desktop 6.2.2 and 6.3.0 on Linux.

PS. I haven't looked at the log output closely, but I tried refreshing and reverting the snap a couple times and had to kill some processes because quiting apparently didn't quit all processes. Hopefully the logs are useful.

Start by reproducing the missing tray/status indicator on Ubuntu 26.04 with GNOME 50.1, comparing Mattermost Desktop 6.3.0 and 6.2.2 from Snap. Use the supplied logs and regression details to narrow the Electron desktop tray behavior; done means the indicator appears in 6.3.0 without breaking other supported platforms.

Written by the indexing model from the issue text.