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_symbol_archive_lib.py

@@ -255,7 +255,7 @@ def test_upsert_forces_sync_exchange_key():
         db = Path(td) / "archive.db"
         init_db(db)
         upsert_trades_cache(
-            "gate_bot",
+            "gate",
             [
                 {
                     "id": 77,
@@ -270,9 +270,9 @@ def test_upsert_forces_sync_exchange_key():
             ],
             db_path=db,
         )
-        rows = load_symbol_trades("gate_bot", "ETH/USDT", db_path=db)
+        rows = load_symbol_trades("gate", "ETH/USDT", db_path=db)
         assert len(rows) == 1
-        assert rows[0]["exchange_key"] == "gate_bot"
+        assert rows[0]["exchange_key"] == "gate"
         assert "account_exchange_key" not in rows[0]