feat: improve replay workflow and viewer UI

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

backend/database.py

@@ -23,6 +23,7 @@ async def init_db():
         if settings.database_url.startswith("sqlite"):
             columns = {
                 "replay_file": "VARCHAR(500)",
+                "replay_url": "VARCHAR(1000)",
                 "chapters_json": "TEXT",
                 "transcode_profile": "VARCHAR(64) NOT NULL DEFAULT 'standard'",
                 "renditions_json": "TEXT",