feat(wallet): 钱包系统替代配额系统，新增支付与退款机制

- 新增钱包余额管理、充值、扣费、退款完整流程
- 新增支付网关抽象层（支持手动/支付宝/微信）
- 用量计费从配额系统迁移到钱包余额扣费
- 新增管理员钱包管理与支付订单管理页面
- 新增用户钱包中心页面
- 移除独立 Key 锁定机制，统一由钱包余额控制
- 新增相关 API 路由、序列化器与数据库迁移
- 新增钱包、支付、退款相关测试

tests/unit/test_wallet_payment_serializers.py

@@ -0,0 +1,68 @@
+from __future__ import annotations
+
+from decimal import Decimal
+from types import SimpleNamespace
+
+from src.api.serializers.wallet_payment import serialize_admin_wallet, serialize_wallet_transaction
+
+
+def test_serialize_wallet_transaction_emits_split_balance_numbers() -> None:
+    tx = SimpleNamespace(
+        id="tx-1",
+        category="adjust",
+        reason_code="adjust_admin",
+        amount=Decimal("1.25"),
+        balance_before=Decimal("5.00"),
+        balance_after=Decimal("6.25"),
+        recharge_balance_before=Decimal("2.00"),
+        recharge_balance_after=Decimal("3.25"),
+        gift_balance_before=Decimal("3.00"),
+        gift_balance_after=Decimal("3.00"),
+        link_type="admin_action",
+        link_id="wallet-1",
+        operator_id="admin-1",
+        description="test",
+        created_at="2026-03-07T00:00:00Z",
+    )
+
+    payload = serialize_wallet_transaction(tx)
+
+    assert payload["recharge_balance_before"] == 2.0
+    assert payload["recharge_balance_after"] == 3.25
+    assert payload["gift_balance_before"] == 3.0
+    assert payload["gift_balance_after"] == 3.0
+
+
+def test_serialize_admin_wallet_omits_version(monkeypatch) -> None:
+    wallet = SimpleNamespace(
+        id="wallet-1",
+        user_id="user-1",
+        api_key_id=None,
+        user=SimpleNamespace(username="alice"),
+        api_key=None,
+        created_at="2026-03-07T00:00:00Z",
+    )
+
+    monkeypatch.setattr(
+        "src.api.serializers.wallet_payment.WalletService.serialize_wallet_summary",
+        lambda _wallet: {
+            "balance": 10.0,
+            "recharge_balance": 7.0,
+            "gift_balance": 3.0,
+            "refundable_balance": 7.0,
+            "currency": "USD",
+            "status": "active",
+            "limit_mode": "finite",
+            "unlimited": False,
+            "total_recharged": 10.0,
+            "total_consumed": 0.0,
+            "total_refunded": 0.0,
+            "total_adjusted": 0.0,
+            "updated_at": "2026-03-07T00:00:00Z",
+        },
+    )
+
+    payload = serialize_admin_wallet(wallet)
+
+    assert "version" not in payload
+    assert payload["owner_name"] == "alice"