Initial commit: Korean voice-cloning TTS prototype

FastAPI backend, web UI, CosyVoice3/F5-TTS setup scripts, and handoff docs for GPU PC continuation.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/tts/base.py

@@ -0,0 +1,18 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from pathlib import Path
+
+
+class TTSEngine(ABC):
+    name: str
+
+    @abstractmethod
+    def synthesize(
+        self,
+        text: str,
+        ref_audio: Path,
+        ref_text: str,
+        out_path: Path,
+    ) -> Path:
+        """단일 텍스트 청크를 WAV로 생성."""