[Subtask] TMS: Bind policy timeTrigger to the expand scheduler #13983

Describe the subtask

On top of #13773 (scheduler pools):

• When a maintenance policy carries non-blank timeTrigger, create / alter / enable keep a matching policy-expand row in scheduled_expand_tasks (task instance id = policy id; due time = next Quartz cron fire)
• Disable, blank timeTrigger, or successful delete remove the row
• Ignore non-maintenance policies
• Expand handler remains a no-op — this subtask only registers / moves / deletes the lease row
• Ensure writes survive the entity-store pool (db-scheduler auto-commit / explicit commit when auto-commit is off)

Out of scope: expand handler implementation (select tables, enqueue cron/commit work), PolicyExpand Spark submit pipeline.

Design: apache/gravitino#13386. Parent: #13760.

PR: #13897

Parent issue

#13760