refactor: 移除 gate_bot，统一为三所架构并更新文档

删除 crypto_monitor_gate_bot 目录，中控与子代理改为 binance/okx/gate 三账户；
文档与 UI 文案「四所」改为「三所」；新增清库前一次性配置备份脚本。

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_hub_fund_history_lib.py

@@ -54,7 +54,7 @@ def test_build_fund_overview_skips_unmonitored(tmp_path, monkeypatch):
     )
     exchanges = [
         {"id": "0", "key": "binance", "name": "Binance", "enabled": True},
-        {"id": "3", "key": "gate_bot", "name": "Gate Bot", "enabled": False},
+        {"id": "2", "key": "gate", "name": "Gate", "enabled": False},
     ]
     board_rows = [
         {