feat: pdf customization: section reordering

[xiaohanyu]

Description

We would like to provide options for users to reorder sections in resume, however, for some core sections like Education, Work, we may need these to stay on the top.

[Optional] Possible solutions

• A reference implementation could check rxresu.me

Acceptance Criteria

• user should be able to re-order sections in frontend dashboard
• the ordering of sections should be persisted in backend as well

Todo list

- [ ] decide whether we allow core sections to be moved to the bottom