feat：新增演示

app/api/public.py

@@ -2,17 +2,59 @@
 
 from typing import Annotated, Any
 
-from fastapi import APIRouter, Query
+from fastapi import APIRouter, Query, Response
 from fastapi.responses import FileResponse
 
-from app.api.screens import Service
+from app.api.screens import Service, thumbnail_url
 from app.common.response import ApiResponse, success_response
+from app.config import settings
 from app.core.exceptions import BizException
-from app.schemas.saved_screen import PublicScreen
+from app.schemas.saved_screen import (
+    DemoScreen,
+    DemoScreenList,
+    PublicScreen,
+    PublishBrief,
+)
 from app.services.screens import LIVE_VARS_MAX_CHARS, public_page
 
 router = APIRouter(prefix="/public", tags=["Public"])
 
+# 演示数据的条数上限和浏览器缓存时长（秒）
+DEMO_LIMIT = 20
+DEMO_CACHE_SECONDS = 60
+
+
+@router.get("/demo/screens")
+async def list_demo_screens(
+    service: Service, response: Response
+) -> ApiResponse[DemoScreenList]:
+    """未登录演示：演示账号（DEMO_OWNER_ID）下的大屏，页面去掉数据源 headers；没配账号时为空"""
+    owner_id = settings.demo_owner_id
+    if owner_id is None:
+        return success_response(DemoScreenList(items=[]))
+    records = await service.list_demo(owner_id, DEMO_LIMIT)
+    response.headers["Cache-Control"] = f"public, max-age={DEMO_CACHE_SECONDS}"
+    return success_response(
+        DemoScreenList(
+            items=[
+                DemoScreen(
+                    screen_id=record.screen_id,
+                    name=record.name,
+                    page=public_page(record.page),
+                    thumbnail_url=thumbnail_url(record.thumbnail),
+                    revision=record.revision,
+                    updated_at=record.updated_at,
+                    publish=None
+                    if record.publish is None
+                    else PublishBrief.model_validate(
+                        record.publish.model_dump(exclude={"revision"})
+                    ),
+                )
+                for record in records
+            ]
+        )
+    )
+
 
 @router.get("/screens/{share_id}")
 async def get_public_screen(