fix(sdk-coin-stx): verify recipient and amount in native STX verifyTransaction

Previously, Stx.verifyTransaction was a near no-op: it only checked that
the recipient count was <= 1. A compromised prebuild could redirect native
STX sends to any address or alter the amount, and local verification
would still pass.

Port the full decode-and-compare pattern from Sip10Token.verifyTransaction
into Stx.verifyTransaction. The new implementation:
- Decodes the prebuild txHex via explainTransaction
- Compares the decoded recipient address (stripping memoId) and amount
  against txParams.recipients[0]
- Compares the memo (from txParams.memo or embedded in the recipient
  address) against the decoded transaction memo
- Validates that the total output amount matches the declared total

This closes the gap where the SIP10 token path already had full recipient
validation but native STX did not, matching the pattern described in
CSHLD-839.

Ticket: CSHLD-839
Session-Id: 7de30368-fc1b-4b09-9d2e-55be78e462dc
Task-Id: 2203e736-35f2-4e2f-8cde-6cdbd0d3e2b6

Author: prajwalu142