v3.7b1: WAV audio support for custom TTS backends

What's New

This beta release adds support for custom TTS backends that return WAV audio instead of MP3 (fixes #58).

Changes

• WAV Detection: Automatically detect WAV format from TTS API response (RIFF header check)
• WAV Chimes: Auto-convert MP3 chimes to WAV on startup for format compatibility
• WAV Conversion: Convert WAV to MP3 when needed for Home Assistant compatibility
• Format Matching: Use matching chime format (WAV chime for WAV TTS) for proper concatenation

Affected Backends

This fix benefits users of custom TTS backends like:

• Chatterbox TTS
• TTS Web UI
• Other OpenAI-compatible endpoints that return WAV

Testing

Please test and report any issues. Install via HACS by selecting "Redownload" → "Show beta versions" → select v3.7b1.