[TTS] Easy Install for AllTalk TTS engine

[Ironship]

Problem

AllTalk TTS requires manual installation (Python, git clone, pip install, server startup). When AllTalk is not running, SE only shows a message with a GitHub link.

Current behavior

IsEngineInstalled() checks if AllTalk server responds within 2 seconds. If not, shows dialog: "AllTalk requires running local AllTalk web server. Read more?" linking to GitHub.

Proposed solution

Add automated installer similar to existing Piper download (DownloadTtsWindow):

1. Detect Python installation (check PATH, common locations)
2. Clone AllTalk repo (https://github.com/erew123/alltalk_tts)
3. Install Python dependencies (pip install -r requirements.txt)
4. Provide "Start AllTalk Server" button that launches the server process
5. Auto-detect when server is ready (poll http://127.0.0.1:7851)
6. Option to auto-start AllTalk when TTS engine is selected

Files affected

• src/UI/Features/Video/TextToSpeech/TextToSpeechViewModel.cs - IsEngineInstalled() flow
• src/UI/Features/Video/TextToSpeech/DownloadTts/ - new AllTalk installer dialog
• src/UI/Logic/Config/SeVideoTextToSpeech.cs - AllTalk install path setting

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Working on this: @Ironship

[niksedk]

Alternately, it might be possible to use e.g. Nuitka to compile to binaries (a lot of work though and the end package might be rather large)

[Ironship]

@niksedk i will try to implement something doing least dependencies. Maybe some kind of "deployment script" as an extension maintained outside of project so it could be droped easly in case of issues