Merge branch 'refactor/backend-architecture' into development

api/app/ports/tts.py

@@ -0,0 +1,10 @@
+"""TTSProvider port — 文字转语音能力契约。"""
+
+from typing import Protocol, runtime_checkable
+
+
+@runtime_checkable
+class TTSProvider(Protocol):
+    async def synthesize(self, text: str, voice: str = "alloy") -> bytes:
+        """Convert text to speech audio bytes."""
+        ...