music-lab: 가사 저장/수정/삭제 CRUD API 추가

- saved_lyrics 테이블 (id, title, text, prompt, created_at, updated_at)
- GET /api/music/lyrics/library — 저장된 가사 목록 조회
- POST /api/music/lyrics/library — 가사 저장
- PUT /api/music/lyrics/library/:id — 가사 수정
- DELETE /api/music/lyrics/library/:id — 가사 삭제

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

music-lab/app/main.py

@@ -10,6 +10,7 @@ from .db import (
     create_task, get_task,
     get_all_tracks, add_track, delete_track, get_track_file_path, get_track_by_task_id,
     update_track_duration,
+    get_all_lyrics, add_lyrics, update_lyrics, delete_lyrics,
 )
 from .local_provider import run_local_generation
 from .suno_provider import (
@@ -332,3 +333,47 @@ def vocal_removal(req: VocalRemovalRequest, background_tasks: BackgroundTasks):
     create_task(task_id, params, provider="suno")
     background_tasks.add_task(run_vocal_removal, task_id, params)
     return {"task_id": task_id, "provider": "suno"}
+
+
+# ── 저장된 가사 CRUD API ────────────────────────────────────────────────────
+
+class LyricsSave(BaseModel):
+    title: str = ""
+    text: str = ""
+    prompt: str = ""
+
+
+class LyricsUpdate(BaseModel):
+    title: Optional[str] = None
+    text: Optional[str] = None
+    prompt: Optional[str] = None
+
+
+@app.get("/api/music/lyrics/library")
+def list_saved_lyrics():
+    """저장된 가사 목록 전체 조회 (생성일 내림차순)."""
+    return {"lyrics": get_all_lyrics()}
+
+
+@app.post("/api/music/lyrics/library", status_code=201)
+def save_lyrics(req: LyricsSave):
+    """가사 저장."""
+    return add_lyrics(req.model_dump())
+
+
+@app.put("/api/music/lyrics/library/{lyrics_id}")
+def edit_lyrics(lyrics_id: int, req: LyricsUpdate):
+    """가사 수정."""
+    data = {k: v for k, v in req.model_dump().items() if v is not None}
+    result = update_lyrics(lyrics_id, data)
+    if not result:
+        raise HTTPException(status_code=404, detail="Lyrics not found")
+    return result
+
+
+@app.delete("/api/music/lyrics/library/{lyrics_id}")
+def remove_lyrics(lyrics_id: int):
+    """가사 삭제."""
+    if not delete_lyrics(lyrics_id):
+        raise HTTPException(status_code=404, detail="Lyrics not found")
+    return {"ok": True}