Implement optimistic UI updates for admin role assignment

[Lakes41]

Difficulty: Advanced | Type: Feature / Performance

Background: POST /v1/members/:address/roles assigns a role to a member from the admin dashboard.

Problem: Without optimistic updates, the admin sees no immediate feedback in the member list/detail view until the round-trip completes, which feels sluggish especially over a real network in live mode.

Expected Outcome: The UI immediately reflects the intended role change optimistically, then reconciles with the server response — rolling back cleanly and showing an error toast (from #20) if the mutation actually fails.

Suggested Implementation: Use React Query's useMutation onMutate/onError/onSettled lifecycle to snapshot and optimistically update the relevant cached member record, rolling back to the snapshot on failure, building on the query-key strategy from #22.

Acceptance Criteria:

• Role change appears instantly in the UI on submit.
• A simulated failure (mock mode error scenario) correctly rolls back the optimistic change and shows an error.
• No duplicate/ghost roles appear after a slow-but-successful mutation.

Likely Affected Files/Directories: app/admin/*, lib/api/

Labels: feature, performance, GrantFox OSS, Maybe Rewarded, Official Campaign | FWC26

[didi168]

I'd like to take this issue on.

The role assignment flow is a good candidate for optimistic updates since admins already know the intended outcome when they submit the change. My plan is to use React Query's mutation lifecycle ("onMutate", "onError", and "onSettled") to update the relevant member data immediately, then reconcile with the server response once the request completes.

I'll make sure failed mutations cleanly roll back to the previous state and surface an error notification, while also testing slow-success and failure scenarios to prevent duplicate or stale role data from appearing in the UI.

I've worked extensively with React Query and optimistic UI patterns, and I'm confident I can implement this in a way that feels responsive while keeping cache consistency intact.

[cristianFleita]

Hello, I'd like to tackle this one

[grantfox-oss]

🦊 GrantFox — @didi168 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #243)
2. Your PR will be reviewed by the Adamantine-guild maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@didi168's PR #311 was approved and merged by @Lakes41.

🏆 @didi168: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (191 total points). Track your full progress on GrantFox.

👏 Great work, @didi168! Keep contributing to Adamantine-guild.