Support MARKET order type

[alexex10]

Changes

• Add support for MARKET order type (order_type=OrderType.MARKET)

(next one is CONDITIONAL, then iteration on refactoring the entire code/SDK API structure)

[2026-03-27 17:14:47,951 81025 8490803776 DEBUG] Sending GET https://api.starknet.sepolia.extended.exchange/api/v1/info/markets?
[2026-03-27 17:14:49,235 81025 8490803776 DEBUG] Sending GET https://api.starknet.sepolia.extended.exchange/api/v1/info/markets/BTC-USD/stats
[2026-03-27 17:14:49,443 81025 8490803776 INFO] Creating MARKET order object for market: BTC-USD
[2026-03-27 17:14:49,443 81025 8490803776 INFO] Placing order...
[2026-03-27 17:14:49,443 81025 8490803776 DEBUG] Placing an order: id=1596207797214642833122240413721618736308962126210297969523593614700790259509
[2026-03-27 17:14:49,443 81025 8490803776 DEBUG] Sending POST https://api.starknet.sepolia.extended.exchange/api/v1/user/order, headers={<RequestHeader.ACCEPT: 'Accept'>: 'application/json', <RequestHeader.CONTENT_TYPE: 'Content-Type'>: 'application/json', <RequestHeader.USER_AGENT: 'User-Agent'>: 'X10PythonTradingClient/1.0.0', <RequestHeader.API_KEY: 'X-Api-Key'>: '6c9a7ffba37265164ee37e6ccf78cd85'}
[2026-03-27 17:14:50,253 81025 8490803776 INFO] Order is placed: {
    "status": "OK",
    "data": {
        "id": 2037518709813129216,
        "external_id": "1596207797214642833122240413721618736308962126210297969523593614700790259509"
    },
    "error": null,
    "pagination": null
}

[alexex10]

explicit for now