test(wallet): add full useStellarWallet hook coverage (#68)

[benzy018]

Description

Closes ecotask-network#68

Adds comprehensive test coverage for src/hooks/useStellarWallet.ts, the primary interface between the app and the Stellar blockchain (Freighter connection, Lobstr deep-link, in-app wallet creation, import, balance refresh, and disconnection).

Extends the existing src/__tests__/useStellarWallet.test.tsx (which covered connect-rollback on balance-fetch failure) with the remaining acceptance criteria:

• connectFreighter: success, extension not detected, extension not unlocked
• connectLobstr: success (public key extracted from signed challenge), not installed, signing cancelled
• createInAppWallet: success + network failure (already covered)
• importWallet: valid key (trims + persists to vault), invalid key (rejected, nothing persisted)
• disconnectWallet: clears the vault entry and resets the store
• refreshBalance / refreshEcoBalance / refreshUsdcBalance: success updates balances, failures keep last known balance

Mocks used: stellar.ts (getBalance, getTokenBalance, createTestnetAccount, isValidSecretKey, getPublicKeyFromSecret, Keypair, TransactionBuilder), lobstr.ts (isLobstrInstalled, openLobstrForSigning), walletVault.ts (via mocked MMKV), and the Zustand useWalletStore.

Type of Change

• Chore (deps, tooling, refactoring)

How Has This Been Tested?

• Unit tests added / updated

Verified: npm test (42 suites, 373 tests pass), npm run typecheck, npx eslint src/__tests__/useStellarWallet.test.tsx — all green.

Checklist

• My code follows the project's code style
• I have performed a self-review of my own code
• I have commented on complex or non-obvious code
• I have updated the documentation where needed
• My changes generate no new warnings or lint errors
• All existing and new tests pass

[benzy018]

Superseded by ecotask-network#118 (this repo is a fork; CI runs on the upstream and the issue ecotask-network#68 lives there).