HB-21 Fix request deliverable modal scroll / overflow behavior

- Type: Bug
- Priority: P2
- Source: bug-photo p12 bottom
- Problem:
- The request-deliverable modal is called out for broken scrolling.
- This makes a working feature feel incomplete or unusable on smaller screens.
- Acceptance criteria:
- Long request forms remain fully accessible without clipped inputs or hidden CTA buttons.
- Modal content scrolls independently when needed on laptop and mobile viewport sizes.
- Likely touched areas:
- `likelee-ui/src/components/agency/AgencyDeliverablesView.tsx`
- shared dialog / sheet styles if the issue is systemic