feat: add CAMB AI TTS integration

[neilruaro-camb]

Hi there! 👋

We're the team at CAMB AI — we build localization and text-to-speech technology and are the localization engine of choice for sports brands like the Premier League, the NBA, NASCAR, and the Australian Open.

We'd love to contribute a CAMB AI TTS integration to SoniTranslate. This PR adds CAMB AI as a new TTS engine alongside the existing options (Edge TTS, OpenAI, Bark, etc.).

What's included

• Dynamic voice fetching — Voices are loaded from the CAMB AI API at startup (GET /list-voices), so users see all available voices in the TTS dropdown without any hardcoding
• Cross-lingual TTS — Any voice works with any supported target language. The language is mapped automatically from SoniTranslate's target language setting to CAMB's locale format
• .env support — The CAMB_API_KEY is read from a .env file via python-dotenv
• Audio compatibility fix — The video mux step now encodes audio as AAC instead of copying MP3 streams, which fixes playback on macOS/QuickTime

Supported languages

Arabic, Bengali, Chinese, Dutch, English, French, German, Hindi, Indonesian, Italian, Japanese, Korean, Polish, Portuguese, Russian, Spanish, Tamil, Telugu, Turkish

Usage

1. Set CAMB_API_KEY in your .env file (get one at camb.ai)
2. Launch SoniTranslate
3. Select any CAMB-TTS voice from the TTS speaker dropdown

We'd be happy to iterate on any feedback. Thanks for building such a great project!