refactor: use custom worker script instead of standard RQ CLI

- Add scripts/rq-docker for Docker container compatibility
- Update Dockerfile to copy scripts directory
- Replace standard rq worker command with custom worker script
- Custom worker includes built-in scheduling via _drain_ready_scheduled_tasks

Co-authored-by: abhi1693 <5083532+abhi1693@users.noreply.github.com>

backend/Dockerfile

@@ -42,6 +42,10 @@ COPY backend/app ./app
 # In-repo these live at `backend/templates/`; runtime path is `/app/templates`.
 COPY backend/templates ./templates
 
+# Copy worker scripts.
+# In-repo these live at `scripts/`; runtime path is `/app/scripts`.
+COPY scripts ./scripts
+
 # Default API port
 EXPOSE 8000