Provide alternative (high-volume responses) pathway for clients without permission to "write files" from browser

## Context

**What if they are blocked by the department or browser to write/modify files?**

https://docs.google.com/document/d/1FUa0_sxK1Nhx2HLDQjnf2bTUE27B56EO_p3u0U4_zos/edit?tab=t.0#bookmark=id.9y80yjq92dxw

## Scenarios to consider

### Previously downloading/confirming (<150 responses) via UI

- [ ] From classic UI download (HTML or CSV) --> New high-volume PKI response flow (WITH "write files" permissions)
- [ ] From classic UI download (HTML or CSV) --> New high-volume PKI response flow (NO "write files" permissions)
- [ ] From classic UI download (enhanced JSON) --> New high-volume PKI response flow (WITH "write files" permissions)
- [ ] From classic UI download (enhanced JSON) --> New high-volume PKI response flow (NO "write files" permissions)

### Previously retrieving (high-volume/attachment) responses via PILOT
- [ ] From Pilot UI/API download --> New high-volume PKI response flow (WITH "write files" permissions)
- [ ] From Pilot UI/API download --> New high-volume PKI response flow (NO "write files" permissions)

### Previously using or planning to use the API as a developer
- [ ] From Programmatic API retrieval --> New high-volume PKI response flow (WITH "write files" permissions)
- [ ] From Programmatic API retrieval --> New high-volume PKI response flow (NO "write files" permissions)

### Previously using email delivery (legacy) on published forms
- [ ] From Email delivery --> New high-volume PKI response flow (WITH "write files" permissions)
- [ ] From Email delivery --> New high-volume PKI response flow (NO "write files" permissions)

### Previously not using GC Forms or not getting responses yet
- [ ] From first time user getting responses --> New high-volume PKI response flow (WITH "write files" permissions)
- [ ] From first time user getting responses --> New high-volume PKI response flow (NO "write files" permissions)

### Previously using the old flow in different ways that need to be addressed
- [ ] Selecting specific responses or groups of responses
- [ ] Working with multiple collaborators to retrieve responses
- [ ] Getting notified of overdue responses on forms
- [ ] Using the Response page to visibly track responses