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/services/test_user_service_delete_user.py

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+from __future__ import annotations
+
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+import pytest
+
+from src.models.database import PaymentOrder, RefundRequest, User, Wallet
+from src.services.user.service import UserService
+
+
+def test_delete_user_blocks_when_unfinished_refund_exists() -> None:
+    user = SimpleNamespace(id="user-1", email="u1@example.com")
+
+    user_query = MagicMock()
+    user_query.filter.return_value = user_query
+    user_query.first.return_value = user
+
+    wallet_ids_query = MagicMock()
+    wallet_ids_query.outerjoin.return_value = wallet_ids_query
+    wallet_ids_query.filter.return_value = wallet_ids_query
+    wallet_ids_query.all.return_value = [("wallet-1",)]
+
+    refund_query = MagicMock()
+    refund_query.filter.return_value = refund_query
+    refund_query.count.return_value = 1
+
+    db = MagicMock()
+    db.in_transaction.return_value = True
+
+    def _query(model: object) -> MagicMock:
+        if model is User:
+            return user_query
+        if model is Wallet.id:
+            return wallet_ids_query
+        if model is RefundRequest:
+            return refund_query
+        raise AssertionError(f"unexpected query target: {model}")
+
+    db.query.side_effect = _query
+
+    with pytest.raises(ValueError, match="未完结退款"):
+        UserService.delete_user.__wrapped__(db, "user-1")
+
+    db.delete.assert_not_called()
+
+
+def test_delete_user_blocks_when_unfinished_payment_order_exists() -> None:
+    user = SimpleNamespace(id="user-2", email="u2@example.com")
+
+    user_query = MagicMock()
+    user_query.filter.return_value = user_query
+    user_query.first.return_value = user
+
+    wallet_ids_query = MagicMock()
+    wallet_ids_query.outerjoin.return_value = wallet_ids_query
+    wallet_ids_query.filter.return_value = wallet_ids_query
+    wallet_ids_query.all.return_value = [("wallet-2",)]
+
+    refund_query = MagicMock()
+    refund_query.filter.return_value = refund_query
+    refund_query.count.return_value = 0
+
+    order_query = MagicMock()
+    order_query.filter.return_value = order_query
+    order_query.count.return_value = 2
+
+    db = MagicMock()
+    db.in_transaction.return_value = True
+
+    def _query(model: object) -> MagicMock:
+        if model is User:
+            return user_query
+        if model is Wallet.id:
+            return wallet_ids_query
+        if model is RefundRequest:
+            return refund_query
+        if model is PaymentOrder:
+            return order_query
+        raise AssertionError(f"unexpected query target: {model}")
+
+    db.query.side_effect = _query
+
+    with pytest.raises(ValueError, match="未完结充值订单"):
+        UserService.delete_user.__wrapped__(db, "user-2")
+
+    db.delete.assert_not_called()