feat: add query order endpoint

[Vinayak1337]

Fixes #85

What changed

• Added a signed GET /openApi/swap/v2/trade/order endpoint for querying one order.
• Exposed the endpoint through TradeService.queryOrder.
• Supported both orderId and clientOrderId query paths.
• Added focused tests for service dispatch, request shape, and client-order-id handling.
• Marked the README feature checkbox as supported.
• Removed one unused import so lint passes.

Tests

• npm test -- trade.service.spec.ts
• npm run lint
• npm run build