[Bug]: Unicode emojis not displaying

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

6.0.0

### Operating System

Windows 11 x64

### Mattermost Server Version

10.5.14

### Steps to reproduce

Send a message using a Unicode emoji e.g. 🫠

### Expected behavior

See the Unicode emoji displayed properly

### Observed behavior

A rectangular box is displayed instead

### Log Output

```shell
[2025-11-14 07:53:44.763] [info] [UpdateManager] Downloaded version 6.0.0
[2025-11-14 07:53:49.101] [info] [UpdateManager] Install on explicit quitAndInstall
[2025-11-14 07:53:49.101] [info] [UpdateManager] Install: isSilent: false, isForceRunAfter: true
[2025-11-14 07:53:49.101] [info] [UpdateManager] Executing: C:\Users\[user]\AppData\Local\mattermost-desktop-updater\pending\mattermost-desktop-setup-6.0.0-win.exe with args: --updated,--force-run
[2025-11-14 07:53:49.747] [info] [UpdateManager] Install on explicit quitAndInstall
[2025-11-14 07:53:49.747] [warn] [UpdateManager] install call ignored: quitAndInstallCalled is set to true
[2025-11-14 07:53:49.762] [info] [UpdateManager] Auto install update on quit
[2025-11-14 07:53:49.762] [info] [UpdateManager] Install: isSilent: true, isForceRunAfter: false
[2025-11-14 07:53:49.762] [info] [UpdateManager] Executing: C:\Users\[user]\AppData\Local\mattermost-desktop-updater\pending\mattermost-desktop-setup-6.0.0-win.exe with args: --updated,/S
[2025-11-14 07:53:55.241] [error] Logger Log level set to: { level: 'info' }
[2025-11-14 07:53:55.382] [info] [Config] Configuration updated to version 4 successfully.
[2025-11-14 07:53:55.429] [warn] [Config] Failed to load configuration file from the filesystem. Using defaults.
[2025-11-14 07:53:55.479] [info] [App.Config] config.autostart has been configured: { autostart: true }
[2025-11-14 07:53:55.479] [info] [App.Config] config.autostart has been configured: { autostart: true }
[2025-11-14 07:53:55.487] [info] [SecureStorage] Secure storage initialized - encryption available
[2025-11-14 07:53:55.495] [info] [SecureStorage] Initialized secure storage cache
[2025-11-14 07:53:55.546] [info] [ServerDropdownView] init
[2025-11-14 07:53:55.556] [info] [App.Initialize] Autoupgrade disabled: true
[2025-11-14 07:53:55.635] [warn] [i18nManager] Failed to set new language { locale: 'en-US' }
[2025-11-14 07:53:55.635] [warn] [i18nManager] Failed to set new language { locale: 'US' }
[2025-11-14 07:53:55.715] [info] [App.Config] config.autostart has been configured: { autostart: true }
[2025-11-14 07:53:55.755] [error] [App.Utils] clearAppCache { err: 'TypeError: Object has been destroyed' }
[2025-11-14 07:53:56.054] [info] [ModalView] [welcomeScreen] preloading with C:\Users\[user]\AppData\Local\Programs\mattermost-desktop\resources\app.asar\internalAPI.js
[2025-11-14 07:53:56.178] [error] [WebContentsEventM...] [renderer] Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'sidebarBg')
[2025-11-14 07:54:07.833] [info] [App.Config] config.autostart has been configured: { autostart: true }
[2025-11-16 10:29:04.382] [info] [WebContentsEventM...] [ea14f88a-2694-491...] [402e85bf-568d-41e...] https://mattermost.web.cern.ch/
[2025-11-17 17:58:38.339] [info] [App.Config] config.autostart has been configured: { autostart: true }
```

### Additional Information

This only occurs on the desktop app and only after updating to 6.0.0. The web app still renders Unicode fine.

Start by reproducing the issue on Windows 11 with Mattermost Desktop 6.0.0, comparing the desktop and web app rendering of 🫠. Trace the desktop renderer and its emoji or font handling to identify where the box appears; done means Unicode emojis display correctly in the desktop app without breaking existing message rendering.

Written by the indexing model from the issue text.