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>

tests/test_preprocess.py

@@ -0,0 +1,13 @@
+from backend.app.text_preprocess import preprocess_korean, split_sentences
+
+
+def test_preprocess_numbers():
+    out = preprocess_korean("예산은 1,250,000원입니다.")
+    assert "원" in out
+    assert "1,250,000" not in out
+
+
+def test_split_sentences():
+    chunks = split_sentences("첫 문장입니다. 두 번째 문장입니다.", max_chars=50)
+    assert len(chunks) >= 1
+    assert all(len(c) <= 50 for c in chunks)