[chidoziemfrancis]

Summary

Adds transactions().list(), wrapping GET /transactions. It takes the same optional ListOptions (limit, offset) introduced for ledgers and balances, sent as query parameters. Unset fields fall back to Core's defaults, which for this route are limit=20 and offset=0.

import com.blnkfinance.blnk.types.ListOptions;

ApiResponse<JsonNode> recent = blnk.transactions().list();
ApiResponse<JsonNode> page = blnk.transactions().list(
    ListOptions.create().limit(100).offset(200));   // GET /transactions?limit=100&offset=200

Core's GetAllTransactions handler silently falls back to its defaults on an invalid limit or offset rather than returning 400. The SDK rejects those values client-side with a 400 instead, so caller mistakes stay visible.

Builds on #, which introduces ListOptions and ListValidators. Once that merges, this PR reduces to a single commit.

Changes

• Transactions: list() and list(ListOptions).
• TransactionsTest: new GET all transactions group with four cases (plain call, query rendering, validation rejection, error handling).
• README.md: paging example extended to transactions, with the differing default noted.
• CHANGELOG.md: bullet under Unreleased.

Test plan

• mvn test offline: 560 run, 0 failures, 57 skipped (live suites gated on BLNK_E2E).