Introduce server TTS support and engine selection while keeping
device TTS as the default.
- Add new persistence keys for storing TTS engine and selected
server voice (ttsEngine, ttsServerVoiceId, ttsServerVoiceName).
- Extend TextToSpeechService to support two engines:
TtsEngine.device (FlutterTts) and TtsEngine.server (remote audio).
- Wire in an AudioPlayer and optional ApiService to fetch raw
audio bytes from the server and play them, with event hooks
mapped to existing lifecycle callbacks.
- Implement fallback to device TTS on server errors or empty
responses, and ensure player lifecycle (pause/stop/dispose)
is handled when using server engine.
- Allow engine and preferred voice to be configured before
initialization and updated at runtime via updateSettings.
This enables selecting a server-side voice and using a remote
TTS provider while preserving compatibility with the existing
device TTS implementation.
- Introduced new preference keys for TTS settings: voice, speech rate, pitch, and volume.
- Updated SettingsService to handle TTS settings and persist them.
- Enhanced AppSettings to include TTS-related properties.
- Implemented TTS settings UI in AppCustomizationPage, allowing users to select voice and adjust speech parameters.
- Added localization support for TTS settings in multiple languages.
- Integrated markdown conversion in TextToSpeechController to clean text before speech synthesis, ensuring only valid content is spoken.
- Updated VoiceCallService to utilize markdown conversion for responses, improving the clarity of spoken content.
- Enhanced VoiceCallPage to display cleaned text from markdown, providing a better user experience during voice interactions.
