修复复盘保存 405：复盘改走成绩更新接口，并修正 API 404 回退。

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

backend/app/main.py

@@ -71,9 +71,17 @@ if dist_dir is not None:
     if assets_dir.is_dir():
         app.mount("/assets", StaticFiles(directory=assets_dir), name="assets")
 
+    @app.api_route(
+        "/api/{rest:path}",
+        methods=["GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS", "HEAD"],
+        include_in_schema=False,
+    )
+    async def api_not_found(rest: str):
+        raise HTTPException(status_code=404, detail="Not Found")
+
     @app.get("/{full_path:path}", include_in_schema=False)
     async def serve_spa(full_path: str):
-        if full_path.startswith("api") or full_path.startswith("api/"):
+        if full_path.startswith("api/") or full_path == "api":
             raise HTTPException(status_code=404, detail="Not Found")
         if full_path in ("", "index.html"):
             return FileResponse(dist_dir / "index.html")