refactor: 重构异步任务系统和计费服务架构

- 重构任务系统：新增 lifecycle (TaskStatus/BillingStatus)、context、application 模块
- 将 video tasks 泛化为 async tasks，支持更通用的异步任务管理
- 新增 Gemini Files 管理模块和管理界面
- 重构 billing 服务：拆分 schema.py 和 service.py
- 新增 candidate 服务模块用于请求候选管理
- 数据库迁移：添加 billing_status、request_id、gemini_file_mappings 表和索引
- 移除废弃的 video_telemetry、task orchestrator 等模块

tests/services/test_video_task_poller.py

@@ -4,14 +4,14 @@ from unittest.mock import AsyncMock, MagicMock
 import pytest
 
 from src.core.api_format.conversion.internal_video import InternalVideoPollResult, VideoStatus
-from src.services.video.task_poller import VideoTaskPollerService
+from src.services.task.impl.video_poller import VideoTaskPollerAdapter
 
 
 @pytest.mark.asyncio
 async def test_poll_task_status_routes_gemini_video_to_gemini(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    poller = VideoTaskPollerService()
+    adapter = VideoTaskPollerAdapter()
 
     task = SimpleNamespace(
         endpoint_id="e1",
@@ -22,24 +22,24 @@ async def test_poll_task_status_routes_gemini_video_to_gemini(
     endpoint = SimpleNamespace(id="e1", base_url="https://example.com", api_format="gemini:video")
     key = SimpleNamespace(id="k1", api_key="enc")
 
-    monkeypatch.setattr(poller, "_get_endpoint", lambda _db, _id: endpoint)
-    monkeypatch.setattr(poller, "_get_key", lambda _db, _id: key)
+    monkeypatch.setattr(adapter, "_get_endpoint", lambda _db, _id: endpoint)
+    monkeypatch.setattr(adapter, "_get_key", lambda _db, _id: key)
     monkeypatch.setattr(
-        "src.services.video.task_poller.crypto_service.decrypt", lambda _v: "decrypted"
+        "src.services.task.impl.video_poller.crypto_service.decrypt", lambda _v: "decrypted"
     )
 
     auth_info = SimpleNamespace(auth_header="authorization", auth_value="Bearer x")
     monkeypatch.setattr(
-        "src.services.video.task_poller.get_provider_auth",
+        "src.services.task.impl.video_poller.get_provider_auth",
         AsyncMock(return_value=auth_info),
     )
 
     poll_gemini = AsyncMock(return_value=InternalVideoPollResult(status=VideoStatus.PROCESSING))
     poll_openai = AsyncMock(return_value=InternalVideoPollResult(status=VideoStatus.PROCESSING))
-    monkeypatch.setattr(poller, "_poll_gemini", poll_gemini)
-    monkeypatch.setattr(poller, "_poll_openai", poll_openai)
+    monkeypatch.setattr(adapter, "_poll_gemini", poll_gemini)
+    monkeypatch.setattr(adapter, "_poll_openai", poll_openai)
 
-    result = await poller._poll_task_status(MagicMock(), task)
+    result = await adapter._poll_task_status(MagicMock(), task)
     assert result.status == VideoStatus.PROCESSING
     assert poll_gemini.await_count == 1
     assert poll_openai.await_count == 0