feat(pool): 记录并展示 Provider Key 累计 Token 与费用

Closes #219

Co-authored-by: AAEE86 <ppk0227@hotmail.com>

tests/unit/test_admin_pool_money_serialization.py

@@ -0,0 +1,11 @@
+from __future__ import annotations
+
+from decimal import Decimal
+
+from src.api.admin.pool.routes import _serialize_money
+
+
+def test_serialize_money_preserves_storage_precision() -> None:
+    assert _serialize_money(Decimal("12.34")) == "12.34000000"
+    assert _serialize_money("0.00000001") == "0.00000001"
+    assert _serialize_money(None) == "0.00000000"