refactor: 共享请求管道、按需懒加载、流式内存护栏与连接池治理

- 抽取 ApiRequestPipeline 单例，44 个路由文件共享同一实例
- Handler/Adapter 模块级 __getattr__ 延迟导入，减少启动时间
- 新增 ensure_stream_buffer_limit() 流式内存护栏（16MB 单行 / 32MB 总量）
- HTTP 空闲连接清理与 curl_cffi LRU 会话池
- ensure_providers_bootstrapped 按需引导指定 provider_types
- Usage 事件序列化迁移至 msgpack，Redis codec 隔离
- 启动预热任务（/readyz 就绪门控）与优雅关闭
- 通知邮件模块独立开关与 SMTP 配置校验
- CryptoService DCL 线程安全修复
- 通知模块开关 DB 查询 30s 内存缓存
- /readyz 对 unknown 状态返回 503
- 预热关闭 5s 超时保护
- 预热适配器逐个 try-except 容错
- FormatConversionRegistry 哨兵模式防并发重复物化
- 流式缓冲检查无条件执行

Closes #230

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

tests/unit/test_notification_email_module_toggle.py

@@ -0,0 +1,164 @@
+from __future__ import annotations
+
+import time
+from types import SimpleNamespace
+from typing import Any, cast
+from unittest.mock import AsyncMock
+
+import pytest
+from fastapi import HTTPException
+from starlette.requests import Request
+
+import src.database as database_module
+from src.middleware.plugin_middleware import PluginMiddleware
+from src.modules.notification_email import notification_email_module
+from src.services.system.config import SystemConfigService
+
+
+def _build_request(path: str = "/boom") -> Request:
+    scope = {
+        "type": "http",
+        "asgi": {"version": "3.0"},
+        "http_version": "1.1",
+        "method": "GET",
+        "scheme": "http",
+        "path": path,
+        "raw_path": path.encode("utf-8"),
+        "query_string": b"",
+        "headers": [],
+        "client": ("127.0.0.1", 12345),
+        "server": ("testserver", 80),
+    }
+    return Request(scope)
+
+
+async def _dummy_app(scope, receive, send):  # type: ignore[no-untyped-def]
+    return
+
+
+def test_notification_email_module_validate_config_requires_smtp(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(
+        "src.services.email.email_sender.EmailSenderService.is_smtp_configured",
+        lambda _db: False,
+    )
+    assert notification_email_module.validate_config is not None
+    ok, message = notification_email_module.validate_config(object())  # type: ignore[arg-type]
+    assert ok is False
+    assert "SMTP" in message
+
+
+@pytest.mark.asyncio
+async def test_call_error_plugins_skips_when_module_disabled(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    middleware = PluginMiddleware(_dummy_app)
+    send_error = AsyncMock()
+    middleware.plugin_manager = cast(
+        Any,
+        SimpleNamespace(
+            get_plugin=lambda *_args, **_kwargs: SimpleNamespace(
+                enabled=True, send_error=send_error
+            )
+        ),
+    )
+    monkeypatch.setattr(
+        middleware,
+        "_is_notification_email_module_enabled",
+        AsyncMock(return_value=False),
+    )
+
+    await middleware._call_error_plugins(
+        _build_request(),
+        RuntimeError("boom"),
+        start_time=time.time(),
+    )
+
+    send_error.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_call_error_plugins_sends_when_module_enabled(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    middleware = PluginMiddleware(_dummy_app)
+    send_error = AsyncMock()
+    middleware.plugin_manager = cast(
+        Any,
+        SimpleNamespace(
+            get_plugin=lambda *_args, **_kwargs: SimpleNamespace(
+                enabled=True, send_error=send_error
+            )
+        ),
+    )
+    monkeypatch.setattr(
+        middleware,
+        "_is_notification_email_module_enabled",
+        AsyncMock(return_value=True),
+    )
+    request = _build_request("/internal-error")
+    request.state.request_id = "req-1"
+
+    await middleware._call_error_plugins(
+        request,
+        RuntimeError("boom"),
+        start_time=time.time(),
+    )
+
+    send_error.assert_awaited_once()
+    assert send_error.await_args is not None
+    kwargs = send_error.await_args.kwargs
+    assert kwargs["context"]["endpoint"] == "GET /internal-error"
+    assert kwargs["context"]["request_id"] == "req-1"
+
+
+@pytest.mark.asyncio
+async def test_notification_email_switch_reads_from_system_config(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    middleware = PluginMiddleware(_dummy_app)
+    request = _build_request("/x")
+
+    class _FakeDb:
+        closed = False
+
+        def close(self) -> None:
+            self.closed = True
+
+    fake_db = _FakeDb()
+    monkeypatch.setattr(database_module, "create_session", lambda: fake_db)
+    monkeypatch.setattr(SystemConfigService, "get_config", lambda *_args, **_kwargs: True)
+
+    enabled = await middleware._is_notification_email_module_enabled(request)
+    assert enabled is True
+    assert fake_db.closed is True
+
+
+@pytest.mark.asyncio
+async def test_call_error_plugins_ignores_http_4xx(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    middleware = PluginMiddleware(_dummy_app)
+    send_error = AsyncMock()
+    middleware.plugin_manager = cast(
+        Any,
+        SimpleNamespace(
+            get_plugin=lambda *_args, **_kwargs: SimpleNamespace(
+                enabled=True, send_error=send_error
+            )
+        ),
+    )
+    monkeypatch.setattr(
+        middleware,
+        "_is_notification_email_module_enabled",
+        AsyncMock(return_value=True),
+    )
+
+    await middleware._call_error_plugins(
+        _build_request(),
+        HTTPException(status_code=400, detail="bad request"),
+        start_time=time.time(),
+    )
+
+    send_error.assert_not_awaited()