chore: 将后端移动到 api/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/prompt/url.py

@@ -0,0 +1,15 @@
+from collections.abc import Callable
+from typing import Any, cast
+
+from django.urls import path
+from django.urls.resolvers import URLPattern, URLResolver
+
+from .consumers import PromptConsumer, GuidanceConsumer
+
+AsgiApplication = Callable[..., Any]
+RoutePattern = URLPattern | URLResolver
+
+websocket_urlpatterns: list[RoutePattern] = [
+    path("ws/prompt/<int:task_id>/", cast(AsgiApplication, PromptConsumer.as_asgi())),
+    path("ws/guidance/<int:task_id>/", cast(AsgiApplication, GuidanceConsumer.as_asgi())),
+]