refactor: 移除启动缓存预热功能

删除 cache_warmup.py 及相关配置项和测试，简化启动流程

tests/services/test_startup_toggles.py

@@ -5,54 +5,11 @@ from types import SimpleNamespace
 
 import pytest
 
-import src.services.system.cache_warmup as cache_warmup_module
 import src.services.system.maintenance_scheduler as maintenance_scheduler_module
 from src.config.settings import config
 from src.services.system.maintenance_scheduler import MaintenanceScheduler
 
 
-@pytest.mark.asyncio
-async def test_start_cache_warmup_skips_task_when_disabled(monkeypatch: pytest.MonkeyPatch) -> None:
-    monkeypatch.setattr(config, "cache_warmup_enabled", False)
-
-    created = False
-
-    def fake_create_task(coro):  # type: ignore[no-untyped-def]
-        nonlocal created
-        created = True
-        if inspect.iscoroutine(coro):
-            coro.close()
-        return object()
-
-    monkeypatch.setattr(cache_warmup_module.asyncio, "create_task", fake_create_task)
-
-    await cache_warmup_module.start_cache_warmup()
-
-    assert created is False
-
-
-@pytest.mark.asyncio
-async def test_start_cache_warmup_creates_task_when_enabled(
-    monkeypatch: pytest.MonkeyPatch,
-) -> None:
-    monkeypatch.setattr(config, "cache_warmup_enabled", True)
-
-    created = False
-
-    def fake_create_task(coro):  # type: ignore[no-untyped-def]
-        nonlocal created
-        created = True
-        if inspect.iscoroutine(coro):
-            coro.close()
-        return object()
-
-    monkeypatch.setattr(cache_warmup_module.asyncio, "create_task", fake_create_task)
-
-    await cache_warmup_module.start_cache_warmup()
-
-    assert created is True
-
-
 @pytest.mark.asyncio
 async def test_maintenance_scheduler_start_skips_startup_task_when_disabled(
     monkeypatch: pytest.MonkeyPatch,