perf: cut offline wallet startup from 60s+ to ~3s

[kaloudis]

Description

When the device is offline, Zeus's LDK Node and Cashu init paths used to block on a series of internal HTTP timeouts — VSS dual-store build (30–60s), node.syncWallets() Esplora + RGS fetch (~30s+), and on a fresh recovery, the sequential Nostr relay loop (8 × 10s = up to 80s). End-to-end an offline cold-start could take 60s+ for an existing wallet and several minutes for a fresh recovery.

This PR seeds connectivityStore.isOffline before any wallet implementation init runs, then short-circuits the network-bound work that would otherwise stall on those internal timeouts. Online cold-start is unchanged apart from a one-time probe capped at ~1.5s.

Impact

Path	Before	After
Initial reachability probe	~5s probe budget	~1.5s
LDK VSS dual-store build (offline)	~30s existing / ~60s restore	skipped
LDK syncWallets() (offline)	~30s+ Esplora + RGS fetch	skipped
Cashu Nostr mint restore (fresh recovery, offline)	up to ~80s sequential	skipped
LDK VSS build timeout when online-but-VSS-slow	30s	10s
Offline cold-start, existing wallet	~60s+	~3s
Offline cold-start, fresh recovery	several minutes	~3s

Online cold-start regresses by at most the new ~1.5s checkNow() probe; when online, the same VSS build and sync paths run as before. As a secondary benefit, online Nostr mint restore now fans out across all relays in parallel instead of trying them one-at-a-time.

Behaviour notes / risks

• VSS deferral while offline. A session built offline uses local-only SQLite. VSS resumes on the next launch once we're online; we do not currently rebuild the node mid-session on reconnect.
• No alerts when offline. When VSS / sync / RGS are skipped because we're offline, vssError / esploraError / rgsError stay undefined, so Wallet.tsx doesn't surface alerts the user already understands. Online failures alert as before.
• Tighter VSS budget. Existing-wallet VSS timeout drops from 30s → 10s. Users on slow connections may occasionally see a vssError alert where the previous 30s budget would have eventually succeeded. The graceful fallback (local-only build, retry on next launch) is unchanged.
• Connectivity ownership. ConnectivityStore lifecycle (start/stop) is now owned by Wallet.fetchData() rather than CashuStore.initializeWallets(). Cashu still registers its reconnect callback via startConnectivityMonitoring.

Test plan

• Offline cold-start, existing wallet — disable Wi-Fi/cellular, launch app; confirm UI is interactive within ~3s and no VSS / Esplora / RGS alerts surface.
• Online cold-start, existing wallet — confirm startup time has not regressed beyond the ~1.5s probe.
• Online → offline mid-session — confirm the running session keeps working off local state; on next cold-start, offline path is taken.
• Offline → online reconnect — confirm connectivityStore.onReconnect fires and Cashu pending tokens sweep.
• Fresh recovery, online — verify Nostr mint restore still finds the backup with parallel fan-out.
• Fresh recovery, offline — verify we no longer hang on the relay loop and the wallet still loads (no mints, as expected).
• VSS reachable but slow — confirm the new 10s budget falls back to local with a clear vssError alert.

PR Type

This pull request is categorized as a:

• New feature
• Bug fix
• Code refactor
• Configuration change
• Locales update
• Quality assurance
• Other

Checklist

• I’ve run yarn run tsc and made sure my code compiles correctly
• I’ve run yarn run lint and made sure my code didn’t contain any problematic patterns
• I’ve run yarn run prettier and made sure my code is formatted correctly
• I’ve run yarn run test and made sure all of the tests pass

Testing

If you modified or added a utility file, did you add new unit tests?

• No, I’m a fool
• Yes
• N/A

I have tested this PR on the following platforms (please specify OS version and phone model/VM):

• Android
• iOS

I have tested this PR with the following types of nodes (please specify node version and API version where appropriate):

On-device

• LDK Node
• Embedded LND

Remote

• LND (REST)
• LND (Lightning Node Connect)
• Core Lightning (CLNRest)
• Nostr Wallet Connect
• LndHub

Locales

• I’ve added new locale text that requires translations
• I’m aware that new translations should be made on the ZEUS Transfix page and not directly to this repo

Third Party Dependencies and Packages

• Contributors will need to run yarn after this PR is merged in
• 3rd party dependencies have been modified:
  • verify that package.json and yarn.lock have been properly updated
  • verify that dependencies are installed for both iOS and Android platforms

Other:

• Changes were made that require an update to the README
• Changes were made that require an update to onboarding

[gemini-code-assist]

Code Review

This pull request optimizes the application's startup performance and offline behavior by introducing a fast connectivity probe and skipping network-dependent tasks like VSS synchronization, wallet syncing, and Nostr mint restoration when offline. Additionally, Nostr mint restoration was refactored to fetch from relays in parallel with a tighter timeout. Feedback suggests adding a guard to prevent redundant callback registrations in CashuStore and implementing error handling when executing reconnect callbacks in ConnectivityStore to ensure robustness.