fix: use TronGrid API to build approve tx with raw_data_hex

[Tristenyang]

Description

TronClientSigner.ensure_allowance() fails when approving token allowance on TRON networks.

The root cause is that tronpy's build() + to_json() produces a transaction dict without raw_data_hex, but
agent-wallet's TronSigner.sign_transaction() requires it:

InsufficientAllowanceError: Approval transaction failed: Tron sign_transaction failed:
Payload must be an unsigned transaction with {raw_data_hex}.

This PR switches from tronpy local transaction building to the TronGrid HTTP API (wallet/triggersmartcontract),
which returns the full transaction object including raw_data_hex. Also uses base58-decoded 41-prefixed hex
addresses for TronGrid API compatibility, and strips the 41 prefix for ABI-encoded parameters.

Closes #64

Tests

• ruff check and ruff format --check pass with no issues
• 189/190 existing tests pass; the 1 failure (test_evm_address_converter_normalizes_to_checksum) is pre-existing on
  main and unrelated to this change
• Manually verified on Tron Nile testnet with bankofai-x402==0.5.8 and bankofai-agent-wallet==2.4.0: token approve

• x402 payment flow completed successfully

Checklist

• I have formatted and linted my code
• All new and existing tests pass
• My commits are signed (required for merge)

[boboliu-1010]

Thanks for the contribution. I checked this against the issue and it does address the immediate raw_data_hex problem, but we’re going with a smaller internal fix instead.

The main reason is that this PR changes the approval success semantics: it treats wallet/broadcasttransaction acceptance as success, while the current implementation waits for the receipt and checks the final execution result on-chain. We want to preserve that behavior to avoid reporting successful approvals for transactions that were only broadcast but later failed during execution.

We’ve opened #66, which fixes the signer payload compatibility issue without changing the existing transaction lifecycle semantics.

Appreciate you identifying the right failure point.