feat: 强化用量计费状态机，新增钱包每日消费汇总分类账

- 将 usage.billing_status 默认值从 settled 改为 pending，完善
  pending -> settled/void 的状态转换逻辑，确保终态不可逆
- 新增 WalletDailyUsageLedger 模型和聚合服务，按账单日汇总
  每个钱包的消费金额、请求数和 token 用量
- 前端钱包中心页面集成每日消费流水展示，支持与充值记录混合
  排序和分页
- 新增两个数据库迁移：修复历史数据状态一致性、创建每日汇总表
- 补充计费状态机单元测试

Closes #218

Co-authored-by: LewisPen <LewisPen@nyadoo.com>

tests/services/test_usage_state_machine.py

@@ -0,0 +1,85 @@
+from types import SimpleNamespace
+from typing import Any
+from unittest.mock import MagicMock
+
+import pytest
+from fastapi import HTTPException
+
+from src.services.task.video.cancel import VideoTaskCancelService
+from src.services.usage.service import UsageService
+
+
+class _DummyQuery:
+    def __init__(self, obj: Any) -> None:
+        self._obj = obj
+
+    def filter(self, *args: Any, **kwargs: Any) -> "_DummyQuery":
+        return self
+
+    def with_for_update(self) -> "_DummyQuery":
+        return self
+
+    def first(self) -> Any:
+        return self._obj
+
+
+def test_update_settled_billing_rejects_terminal_usage() -> None:
+    usage = SimpleNamespace(
+        request_id="req-1",
+        billing_status="settled",
+        finalized_at="2026-03-06T00:00:00+00:00",
+        total_cost_usd=1.23,
+    )
+    db = MagicMock()
+    db.query.return_value = _DummyQuery(usage)
+
+    updated = UsageService.update_settled_billing(
+        db,
+        request_id="req-1",
+        total_cost_usd=2.34,
+        status="completed",
+    )
+
+    assert updated is False
+    assert usage.total_cost_usd == 1.23
+
+
+def test_update_usage_status_skips_terminal_usage() -> None:
+    usage = SimpleNamespace(
+        request_id="req-1",
+        billing_status="settled",
+        finalized_at="2026-03-06T00:00:00+00:00",
+        status="completed",
+        error_message=None,
+        provider_name="demo",
+    )
+    db = MagicMock()
+    db.query.return_value = _DummyQuery(usage)
+
+    result = UsageService.update_usage_status(
+        db=db,
+        request_id="req-1",
+        status="failed",
+        error_message="boom",
+    )
+
+    assert result is usage
+    assert usage.status == "completed"
+    assert usage.error_message is None
+    db.commit.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_task_cancel_rejects_terminal_task() -> None:
+    task = SimpleNamespace(
+        id="t1",
+        user_id="u1",
+        status="completed",
+        request_id="req-1",
+    )
+    svc = VideoTaskCancelService(MagicMock())
+
+    with pytest.raises(HTTPException) as exc:
+        await svc.cancel_task(task=task, task_id="t1")
+
+    assert exc.value.status_code == 409