recetas B3: DELETE /cookbook/{author_id} (opt-out del respaldo, borra solo privadas)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

main.py

@@ -243,6 +243,19 @@ def cookbook(author_id: str, db: Session = Depends(get_db)):
     return [r.to_app() for r in rows]
 
 
+@app.delete("/cookbook/{author_id}")
+def delete_cookbook(author_id: str, db: Session = Depends(get_db)):
+    """Opt-out del respaldo: borra las copias PRIVADAS de un autor. Lo que
+    publicó a propósito (pública / no listada) se mantiene."""
+    n = (
+        db.query(Recipe)
+        .filter(Recipe.author_id == author_id, Recipe.visibility == "private")
+        .delete()
+    )
+    db.commit()
+    return {"deleted": n}
+
+
 @app.post("/recipes")
 def add_recipe(body: RecipeIn, db: Session = Depends(get_db)):
     items = [i.model_dump() for i in body.items]