Replace scopedProperties, which only WalletConnect v2 supports, with a custom
JSON-RPC method that WalletConnect v1 (Pera Connect, Defly Connect) can also
carry, and that could later refresh empty signatures without a reconnect.

- The method is requested in optionalNamespaces, so wallets that don't
  support it still approve the session, and only called if approved
- It's called right after connect with a 30s timeout and never holds up the
  connection; late responses are discarded if the session or network changed
- Restored and updated sessions keep the store's empty signatures; a new
  session starts without any until the wallet answers
- Add BaseWallet.applyEmptySignatures() for adapters to apply a wallet's
  { address: base64 } response consistently

Resolves the conflict in vault.service.spec.ts by taking master's spec and
re-applying the namespace test block on top of it. Master added three Vault
call sites since the branch point (canCreateUserKey, the shared pqRequest
path, kvCreate); they now go through namespaceHeaders() like the rest, and
the header table covers all fourteen.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs: add caveat to lsig off-curve account generation