Prevent failed XDC wallet initialization from breaking Celo top-ups #582

After deployment, XdcAdminWallet failed to initialize because its RPC returned a rate-limit error. Subsequent Celo /verify/topWallet requests failed with:

Cannot read properties of undefined (reading 'methods')

Following #575, the server continues running after wallet initialization fails. However, MultiWallet.isConnected checks all non-Base wallets, and Web3Wallet.isConnected assumes identityContract exists. One uninitialized wallet therefore breaks the entire check.

Requested fix

• Handle an uninitialized wallet without crashing the shared verification check.
• Preserve existing behavior: a positive verification result on any participating Identity chain is sufficient. An unavailable wallet must never count as verified.
• Keep a diagnostic for the unavailable wallet. Do not bypass verification.
  Focused tests
• XDC is uninitialized and Celo positively verifies the account: the check succeeds.
• XDC is uninitialized and no other wallet positively verifies the account: the check does not authorize a top-up.
  Keep this minimal: missing-contract handling and regression tests only. No RPC-provider refactor or automatic retry system. Add XDC RPC failover for identifier verification #581 addresses signature-verification RPC fallback, not this wallet-initialization path