feat: get cheche dir paths

src/utils/__init__.py

@@ -0,0 +1,3 @@
+from ._cache import ensure_cache_dir, get_cache_path
+
+__all__ = ["ensure_cache_dir", "get_cache_path"]

src/utils/_cache.py

@@ -0,0 +1,23 @@
+from pathlib import Path
+
+from ..config import get_cache_dir, get_project_root
+
+
+def ensure_cache_dir() -> Path:
+    env_cache_str = get_cache_dir()
+    env_cache_path = Path(env_cache_str)
+    if env_cache_path.is_absolute():
+        cache_dir = env_cache_path
+    else:
+        project_root = get_project_root()
+        cache_dir = (project_root / env_cache_path).resolve()
+    if not cache_dir.exists():
+        cache_dir.mkdir(parents=True, exist_ok=True)
+    return cache_dir
+
+
+def get_cache_path(filename: str | None = None) -> Path:
+    cache_dir = ensure_cache_dir()
+    if filename is None:
+        return cache_dir
+    return cache_dir / filename