fix(scheduler): default scheduled job timezone to system timezone

Replace hardcoded Asia/Shanghai with host IANA timezone detection for new scheduled jobs across tools, admin API, gateway cron, and store layer.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_scheduler_system_timezone.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import os
+import unittest
+from unittest.mock import patch
+
+from runtime.scheduler.system_timezone import (
+    default_system_timezone,
+    reset_default_system_timezone_cache,
+)
+from zoneinfo import ZoneInfo
+
+
+class SchedulerSystemTimezoneTests(unittest.TestCase):
+    def tearDown(self) -> None:
+        reset_default_system_timezone_cache()
+        os.environ.pop("AIA_SCHEDULER_DEFAULT_TIMEZONE", None)
+        os.environ.pop("TZ", None)
+
+    def test_env_override_wins(self) -> None:
+        os.environ["AIA_SCHEDULER_DEFAULT_TIMEZONE"] = "Europe/Berlin"
+        reset_default_system_timezone_cache()
+        self.assertEqual(default_system_timezone(), "Europe/Berlin")
+
+    def test_windows_registry_maps_to_iana(self) -> None:
+        with patch("runtime.scheduler.system_timezone.sys.platform", "win32"), patch(
+            "runtime.scheduler.system_timezone._windows_system_timezone",
+            return_value="Asia/Jakarta",
+        ):
+            reset_default_system_timezone_cache()
+            self.assertEqual(default_system_timezone(), "Asia/Jakarta")
+
+    def test_default_is_valid_iana(self) -> None:
+        tz = default_system_timezone()
+        ZoneInfo(tz)
+
+
+if __name__ == "__main__":
+    unittest.main()