Mark as conflict when uploaded strings are already translated

### Describe the problem

There are currently three options for conflict handling when uploading translation:

1. Change only untranslated strings
2. Change translated strings
3. Change translated and approved strings

So your uploaded string is either used as translation or discarded. And when discarded, only a number is shown, no detailed report is available.

### Describe the solution you'd like

Add option "Add as suggestion and mark as conflict" for conflict handling:

* Add the uploaded version as suggestion, so your local translation is not lost.
* Also add a dedicated label "Upload conflict" for that string, so the conflicting strings can be located.

### Describe alternatives you've considered

_No response_

### Screenshots

_No response_

### Additional context

_No response_