Voice previews can be wrong over time

[marisademeglio]

Voices saved under preferred voices are not updated when their href changes in the engine. This may be solvable only in the engine, or perhaps there's a way we can adapt to what is necessarily a changing list of voices.

cc @bertfrees just putting this here for safe keeping.

[marisademeglio]

The UI has to switch its approach so that it doesn't store preview or hrefs but grabs them on the fly by cross-referencing the voice name + tts engine from the list given by the pipeline engine.