[Feature Request] Add TP/SL order placement and position-level stop management endpoints #7

Summary

The current MCP server (v1.0.6) is missing critical risk management endpoints.
It is not possible to attach Take Profit or Stop Loss orders to futures positions
— either at the time of opening or after. This makes the server unsuitable for
real trading without manual intervention in the Bitget app after every order.

Missing Endpoints

Reproduction Steps

1. Connect MCP server with valid API credentials (futures trade permission enabled)
2. Open a futures position using futures_place_order with presetStopLossPrice
   and presetTakeProfitPrice parameters
3. Call futures_get_positions — observe stopLoss and takeProfit fields are
   empty strings despite being passed in the order
4. Attempt to set TP/SL after open — no tool available in the MCP server

Expected Behaviour

• futures_place_order should correctly pass and attach preset TP/SL to the order
• A dedicated tool (e.g. futures_set_tpsl) should expose the
  /api/v2/mix/order/place-tpsl-order endpoint for existing positions

Impact

Without TP/SL support, every trade opened via the MCP requires manual risk
management in the Bitget app, which defeats the purpose of AI-driven trading
automation. This is arguably the most critical missing feature for any real
trading use case.

Environment

• MCP Server version: 1.0.6
• Client: Claude Code
• Account mode: Hedge mode, Cross margin, USDT-Futures