#10356: TTS: add Typecast provider (emotion presets, audio tuning, Asian language voices)

## Summary Adds [Typecast](https://typecast.ai?lang=en) by Neosapience as a TTS provider with emotion presets and audio tuning controls. ## What Typecast offers - 7 emotion presets (happy/sad/angry/whisper/toneup/tonedown/normal) with adjustable intensity (0-2x) as API parameters - Audio tuning: volume (0-200%), pitch (±12 semitones), tempo (0.5-2x) - 500+ voices across 37 languages with strong Asian language support - Official TypeScript SDK (@neosapience/typecast-js) - [API Documentation](https://typecast.ai/docs) ## Changes - TtsProvider type + Zod schema with full config validation - typecastTTS() in standard + telephony flows (WAV sample rate parsed from header) - TYPECAST_API_KEY env var, provider fallback order - Gateway RPC + CLI + voice-call extension - Docs (en + zh-CN) ## Risk Opt-in (API key required). Existing provider behavior unchanged. ## Testing pnpm build && pnpm lint clean. Manual: /tts audio Hello with live API key verified.