添加文件监视器地基模块，重构模型请求模块使用新版本的配置热重载模块，新增watchfiles依赖

src/config/file_watcher.py

@@ -0,0 +1,68 @@
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Awaitable, Callable, Iterable, Sequence
+
+from watchfiles import Change, awatch
+
+import asyncio
+
+from src.common.logger import get_logger
+
+
+logger = get_logger("file_watcher")
+
+
+@dataclass(frozen=True)
+class FileChange:
+    change_type: Change
+    path: Path
+
+
+ChangeCallback = Callable[[Sequence[FileChange]], Awaitable[None]]
+
+
+class FileWatcher:
+    def __init__(self, paths: Iterable[Path], debounce_ms: int = 600) -> None:
+        self._paths = [path.resolve() for path in paths]
+        self._debounce_ms = debounce_ms
+        self._running = False
+        self._task: asyncio.Task[None] | None = None
+
+    @property
+    def running(self) -> bool:
+        return self._running
+
+    async def start(self, callback: ChangeCallback) -> None:
+        if self._running:
+            return
+        self._running = True
+        self._task = asyncio.create_task(self._run(callback))
+
+    async def stop(self) -> None:
+        if not self._running:
+            return
+        self._running = False
+        if self._task is None:
+            return
+        self._task.cancel()
+        try:
+            await self._task
+        except asyncio.CancelledError:
+            return
+
+    async def _run(self, callback: ChangeCallback) -> None:
+        try:
+            async for changes in awatch(*self._paths, debounce=self._debounce_ms):
+                if not self._running:
+                    break
+                try:
+                    await callback(self._normalize_changes(changes))
+                except Exception as exc:
+                    logger.warning(f"文件变更回调执行失败: {exc}")
+        except asyncio.CancelledError:
+            return
+        except Exception as exc:
+            logger.error(f"文件监视器运行异常: {exc}")
+
+    def _normalize_changes(self, changes: set[tuple[Change, str]]) -> list[FileChange]:
+        return [FileChange(change_type=change, path=Path(path)) for change, path in changes]