Add summarize feature with LLMs

[JulianFP]

Sometimes you may want to get a summary for a long interview/talk/meeting/... after transcribing them. LLMs a great for this kind of job however they often come with similar privacy issues as whisper (ChatGPT, Gemini, ... are not self-hostable!). If we would provide something like that using a self-hosted LLM like llama or mistral it would make this kind of thing a lot more convenient for the user and prevent them from just copy and pasting the transcript into ChatGPT (and thus eliminating every benefit of this project).