[Feature Request]: Persist language filter selection for masks

### Problem Description

Selecting a given language filter for 'masks' fails to persist between starts, or if you navigate to a chat then back to the masks page. Most of the masks are in chinese and I can't see a way to delete them, so this is a key one for internationalisation.

### Solution Description

1. Persist the language filter in config and persist after restart
2. Allow deletion of the 'built in' masks that lack a delete option.

### Alternatives Considered

_No response_

### Additional Context

_No response_