chore: remove unnecessary Path conversions

Remove unnecessary `pathlib.Path` conversions. (CACHE_DIR and DATA_DIR)

Use `/` Path joining shorthand to ensure using platform specific Path separators (Windows: \\, Unix: /)

backend/open_webui/routers/images.py

@@ -25,7 +25,7 @@ from pydantic import BaseModel
 log = logging.getLogger(__name__)
 log.setLevel(SRC_LOG_LEVELS["IMAGES"])
 
-IMAGE_CACHE_DIR = Path(CACHE_DIR).joinpath("./image/generations/")
+IMAGE_CACHE_DIR = CACHE_DIR / "image" / "generations"
 IMAGE_CACHE_DIR.mkdir(parents=True, exist_ok=True)