fix(panel): wrap default_conf_dir in Path for plan config writes

schedule-intent/schedule-gap concatenated str / str (default_conf_dir
returns str) → 500 on save; schedule_board already wrapped its copy.

web/app.py

@@ -1397,7 +1397,7 @@ def schedule_intent():
         return redirect(url_for("schedule_board"))
     if window and window not in ("morning", "afternoon", "evening"):
         window = ""
-    conf_path = pl.default_conf_dir(pl.default_work_dir()) / "schedule-plan.json"
+    conf_path = Path(pl.default_conf_dir(pl.default_work_dir())) / "schedule-plan.json"
     try:
         conf = json.loads(Path(conf_path).read_text(encoding="utf-8"))
     except (OSError, ValueError):
@@ -1431,7 +1431,7 @@ def schedule_gap():
     if g not in (10, 15, 20, 25, 30, 40, 45, 60, 90, 120):
         flash("间隔值不合法(可选 10/15/20/25/30/40/45/60/90/120 分钟)", "error")
         return redirect(url_for("schedule_board"))
-    conf_path = pl.default_conf_dir(pl.default_work_dir()) / "schedule-plan.json"
+    conf_path = Path(pl.default_conf_dir(pl.default_work_dir())) / "schedule-plan.json"
     try:
         conf = json.loads(Path(conf_path).read_text(encoding="utf-8"))
     except (OSError, ValueError):