feat: improve replay workflow and viewer UI

Co-Authored-By: Claude Fable 5 <[email protected]>

backend/services/stream_service.py

@@ -29,6 +29,7 @@ class StreamService:
                             cover_url: str | None = None,
                             scheduled_at: str | None = None,
                             replay_file: str | None = None,
+                            replay_url: str | None = None,
                             chapters: list[dict] | None = None,
                             transcode_profile: str = "standard",
                             homepage_visible: bool = True,
@@ -45,6 +46,7 @@ class StreamService:
             description=description,
             cover_url=cover_url,
             replay_file=replay_file,
+            replay_url=replay_url,
             chapters_json=json.dumps(chapters or [], ensure_ascii=False),
             transcode_profile=transcode_profile,
             homepage_visible=homepage_visible,