feat(client): SdkWallet — PrivacyWallet over prover + paymaster (#917)

The non-native PrivacyWallet (EVM / legacy-SN via a CallSet signer inside the prover). It composes
the Strk20Prover (proves, owns the viewing key) and the Paymaster (sponsors + broadcasts the fee, so
the user needn't hold the fee token). partialCommitment/strk20PrepareInvoke delegate to the prover.
strk20InvokeTransaction runs the private apply_action flow: quote the fee, fold it in as a withdraw
so the proof covers it, prove, then paymaster broadcasts the proven call. The regular flow (a
deposit's approve, which must run as the user but can't under apply_action where the paymaster is the
executing account — needs invoke_and_apply_action) is deferred: executeWithProof/estimateInvokeFee
reject for now. 6 tests.

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