Font rendering broken when web fonts are disabled

### Steps to reproduce

1. Open the web interface
2. (optionally, log in and open any chat)

### Outcome

#### What did you expect?

Text should be clear and readable.

#### What happened instead?

Font rendering is broken; spacing is completely off, and numbers don't render at all

Screenshot:

(note that the link in the above actually reads `https://bugzilla.mozilla.org/show_bug.cgi?id=1980799`, but numbers are invisible).

### Operating system

Alpine Linux

### Browser information

Firefox 141.0

### URL for webapp

https://chat.mozilla.org/#/room/#introduction:mozilla.org

### Application version

Element version: 1.11.106 Crypto version: Rust SDK 0.12.0 (b30f1f3), Vodozemac 0.9.0

### Homeserver

https://chat.mozilla.org/#/room/#introduction:mozilla.org

### Will you send logs?

Yes