Logical Clash with Flags Combinations

### Describe the issue

The application allows combinations of flags which are invalid.

Untranslatable and Forbidden are mutually exclusive
Untranslatable and Terminology are mutually exclusive
But it is still allowed to even set all three:

### I already tried

- [x] I've read and searched [the documentation](https://docs.weblate.org/).
- [x] I've searched for similar filed issues in this repository.

### Steps to reproduce the behavior

h

### Expected behavior

h

### Screenshots

_No response_

### Exception traceback

```pytb

```

### How do you run Weblate?

Other

### Weblate versions

_No response_

### Weblate deploy checks

```shell

```

### Additional context

_No response_