[Senior] Remove IBEX API dependency from mobile app

[islandbitcoin]

Summary

The Flash mobile app currently depends on IBEX API availability for startup and basic functionality. When IBEX APIs (sandbox or production) are unreachable, the app may fail to load wallets, display balances, or complete transactions that should work independently via the Flash/Galoy backend.

Goal

The mobile app should start and function with BTC-only wallet when IBEX APIs are unavailable. USD features gracefully degrade rather than breaking the entire app experience.

Requirements

• App launches and displays BTC wallet balance without IBEX connectivity
• BTC send/receive flows work end-to-end without any IBEX API calls
• USD wallet UI shows a clear "temporarily unavailable" state (not errors, spinners, or crashes)
• Transaction history renders BTC transactions independently
• Currency conversion display falls back gracefully (show sats-only if USD rate unavailable)
• No splash screen or loading state blocked by IBEX health checks
• Error boundaries catch IBEX-related failures without propagating to BTC flows

Context

• Backend companion issue: flash#302
• Related Linear issues: ENG-223, ENG-236
• IBEX auth deprecation deadline: May 31, 2026 (ENG-38)
• Related: flash-mobile#572 (Reproducibility Issue)

Acceptance Criteria

1. Kill network access to IBEX endpoints → app starts, BTC wallet visible and functional
2. Send BTC to a Lightning invoice with IBEX offline → succeeds
3. USD wallet section shows "USD wallet temporarily unavailable" (not a crash or infinite loader)
4. Restore IBEX connectivity → USD wallet recovers automatically without app restart

[patoo0x]

📋 Definition of Done

⚠️ Bundled bounty: This issue is bundled with flash#302 and #572. See the full DoD and 500,000 sats bounty details on flash#302.

[chengyixu]

Proposal

I'd like to work on the mobile side of this bundled bounty (flash-mobile#591 + flash#302 + flash-mobile#572).

Approach:

• Identify all IBEX initialization calls in the React Native startup sequence
• Add a lightweight IBEX health-check with a 3-second timeout before wallet load; on failure, switch to BTC-only mode
• Implement a WalletCapabilityContext that downstream components subscribe to — USD wallet features render conditionally based on IBEX availability
• Ensure Lightning send/receive, balance fetch (via Galoy backend), and transaction history work fully without IBEX
• Gracefully hide USD wallet UI (not crash) when IBEX is unavailable

Timeline: 2-3 days

Available immediately! cc @patoo0x

[chengyixu]

Proposing to remove the IBEX API dependency from the mobile app.

Analysis of the dependency:
The IBEX APIs are used for two things in the current mobile app:

1. USD wallet balance and transaction routing (Lightning ↔ USD conversion)
2. Startup initialization that blocks BTC wallet display

Proposed approach:

1. Decouple startup from IBEX:

• Move IBEX initialization out of the critical startup path into a lazy-loaded service
• BTC wallet data fetches from Flash/Galoy backend directly — no IBEX needed
• App renders with BTC wallet immediately on launch

2. USD wallet graceful degradation:

• Wrap all IBEX API calls in a useIbexAvailability hook with timeout (5s)
• If unavailable: show USD wallet card with "Service temporarily unavailable" banner (not error/crash)
• BTC wallet continues to function normally regardless

3. Transaction history:

• BTC transactions render from Galoy GraphQL (already working independently)
• USD transactions show cached data or skeleton with status note if IBEX is down

Key files:

• app/screens/home-screen — decouple wallet loading
• app/graphql/ — ensure BTC queries don't chain through IBEX
• Add useIbexHealthCheck hook for graceful USD degradation

Timeline: Can deliver this refactor within 5-7 days given the scope. Ready to start immediately.