[SDK · Network & Horizon] Implement HorizonClient wrapper — submit endpoint

[amina69]

Epic: Network & Horizon
Labels: network, tx, sdk
Size: S (~1 day)

Description

Wrap the Horizon transaction submit endpoint with error normalisation.

Tasks

• submitTransaction(tx: Transaction): submit, return raw result
• Parse Horizon error body for result_codes on 400
• Return {hash, ledger, successful} on success
• On 400: throw HorizonSubmitError with parsed result_codes
• On 504: throw TransactionTimeoutError with retryable:true
• Log submission at info level with txHash (no envelope)
• Unit test: success, 400 with result codes, 504