[UX-001] ~13 screens have silent error and loading states — failures invisible to users

## Summary

**Severity:** P2 — UX Integrity
**Phase:** Phase 5 Remediation (UI/UX Error States)
**Audit Reference:** SPIN Agent Product Integrity Report, Phase 1

## Finding

Approximately 13 screens across the Dashboard do not surface error or loading states to users. When an API call fails or is pending, the screen shows no indicator — no spinner, no error message, no retry prompt. Users experience blank or stale content with no explanation.

## Known Affected Screens (non-exhaustive)

- Mission Profile save (#616)
- Generate SAP button (#624)
- POA&M sub-page for org-scoped systems (#629)
- Remediation task creation (#625, #631)
- Gap Analysis page (#546)
- Auto-fill narratives (#627)
- RMF Roles assign modal (#620)
- System detail load failure (#622)
- Chat quick-actions (#621, #548)

## Acceptance Criteria

- [ ] Audit all Dashboard screens for missing error/loading state handlers
- [ ] Every async operation shows a loading indicator while pending
- [ ] Every failed operation shows a user-readable error message with retry option where applicable
- [ ] Error messages do not expose raw stack traces or internal error codes to end users
- [ ] At minimum, the ~13 screens identified in the Phase 1 audit are remediated

## Related

- See individual bug reports linked above for screen-specific details
- Audit artifact: SPIN Agent Product Integrity Report (Phase 1)

Start by auditing the Dashboard screens listed in the issue, beginning with the linked screen-specific reports (#616, #624, #629, #625, #631, #546, #627, #620, #622, #621, and #548). Verify pending and failed API-call behavior on each screen; done means the identified screens show loading indicators, readable errors, and applicable retry options without raw internal details.

Written by the indexing model from the issue text.