Refactor project structure and enhance backend integration

- Expanded package inclusion in `pyproject.toml` to support new modules.
- Introduced new `adapters` and `protocol` packages for better organization.
- Added backend adapter implementations for control plane integration.
- Updated main application imports to reflect new package structure.
- Removed deprecated core components and adjusted documentation accordingly.
- Enhanced architecture documentation to clarify the new runtime and integration layers.

engine/providers/tts/siliconflow.py

@@ -0,0 +1,8 @@
+"""Backward-compatible imports for legacy siliconflow_tts module."""
+
+from providers.tts.openai_compatible import OpenAICompatibleTTSService, StreamingTTSAdapter
+
+# Backward-compatible alias
+SiliconFlowTTSService = OpenAICompatibleTTSService
+
+__all__ = ["OpenAICompatibleTTSService", "SiliconFlowTTSService", "StreamingTTSAdapter"]