fix: unify task workspace directory resolution

src/biliup_next/infra/workspace_cleanup.py

@@ -1,9 +1,9 @@
 from __future__ import annotations
 
 import shutil
-from pathlib import Path
 
 from biliup_next.infra.task_repository import TaskRepository
+from biliup_next.infra.workspace_paths import resolve_task_work_dir
 
 
 class WorkspaceCleanupService:
@@ -15,7 +15,7 @@ class WorkspaceCleanupService:
         if task is None:
             raise RuntimeError(f"task not found: {task_id}")
 
-        session_dir = Path(str(settings["session_dir"])) / task.title
+        session_dir = resolve_task_work_dir(task)
         removed: list[str] = []
         skipped: list[str] = []