[Feature] Add Scheduled Task Management with Cron Expression Support

[anshul23102]

Summary

daemon manages long-running services but not scheduled or recurring tasks. Adding task scheduling makes daemon a single tool for all background workloads.

Proposed Solution

Add a tasks section to the daemon config:

tasks:
  daily-backup:
    command: "bash scripts/backup.sh"
    schedule: "0 2 * * *"
    timeout: 600
    on_failure: retry
    retry:
      max_attempts: 3
      delay: 60

The scheduler checks every minute whether any task is due. On trigger: spawn the command as a child process, capture stdout/stderr to a task log file, record execution start time, end time, exit code, and status.

daemon tasks list shows all tasks with next scheduled run time. Dashboard "Tasks" tab shows last run result and a "Run Now" button for manual trigger.

Acceptance Criteria

• Tasks run at the correct times per their cron expression.
• daemon tasks list shows all tasks with their next run time.
• Failed tasks with retry configured are retried the specified number of times.
• Task output is captured to a separate log file.
• "Run Now" triggers the task immediately without affecting the scheduled trigger.