feat: Real-time UI updates via WebSocket/SSE subscription (client-side)

[joelpeace48-cell]

Background & current state

The UI polls for updates (frontend/src/hooks/useCampaignPolling.js). Polling is wasteful and laggy. Backend real-time exists/planned (WS #456, Horizon SSE #468), but the frontend doesn't consume a live stream.

Goal

Consume a WebSocket/SSE stream client-side so campaign/participant state updates live, with reconnect/backoff and cache reconciliation.

Technical design

• A subscription client that connects to the backend WS/SSE, dispatches events into the data cache (reconcile with React Query Frontend: Add TanStack Query (React Query) for data fetching and caching #346 if adopted, else local store), and falls back to polling on disconnect.
• Exponential backoff reconnect; dedupe events; update participant counts/claims live.

Edge cases

• Connection drop → backoff reconnect + resume; fall back to polling.
• Out-of-order/duplicate events → idempotent cache updates.
• Many tabs → shared worker or per-tab connection cap.
• Auth for the stream.

Task breakdown

• Subscription client + reconnect/backoff + polling fallback.
• Cache reconciliation for live events.
• Replace/augment useCampaignPolling.
• E2E observing a live update.

Acceptance criteria

• Participant count/claims update live without manual refresh; degrades to polling on disconnect.

Testing & verification

• E2E: trigger a backend event → UI updates without refresh.

Out of scope

• The backend stream (Backend: Add WebSocket server for real-time campaign event streaming #456/Backend: Add Stellar network event subscription via Horizon SSE #468) — consumed here.

Dependencies / related

• Consumes Backend: Add WebSocket server for real-time campaign event streaming #456/Backend: Add Stellar network event subscription via Horizon SSE #468; relates to Frontend: Add TanStack Query (React Query) for data fetching and caching #346.

Difficulty: medium · Effort: M · stellar

[anuoluwaponiorimi]

Hi @maintainer — thanks for the open door to apply again. I'd like to continue contributing and this issue is a good fit. I'll deliver it properly and won't open the PR until CI is fully green. Glad to take it.

[joelpeace48-cell]

I love your work @anuoluwaponiorimi

[grantfox-oss]

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

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #626)
2. Your PR will be reviewed by the FinesseStudioLab maintainers

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