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>

manual_trading_hub/settings_store.py

@@ -54,23 +54,13 @@ DEFAULT_EXCHANGES = [
     {
         "id": "2",
         "key": "gate",
-        "name": "Gate训练 · crypto_monitor_gate",
+        "name": "Gate · crypto_monitor_gate",
         "agent_url": "http://127.0.0.1:15202",
         "flask_url": "http://127.0.0.1:5000",
         "review_url": "http://127.0.0.1:5000/records",
         "enabled": True,
         "capabilities": ["key", "trend"],
     },
-    {
-        "id": "3",
-        "key": "gate_bot",
-        "name": "Gate趋势 · crypto_monitor_gate_bot",
-        "agent_url": "http://127.0.0.1:15203",
-        "flask_url": "http://127.0.0.1:5002",
-        "review_url": "http://127.0.0.1:5002/records",
-        "enabled": True,
-        "capabilities": ["key", "trend"],
-    },
 ]