Add email sending queue with rate limiting to avoid spam behavior

[Elmbark]

Is your feature request related to a problem? Please describe.

When applying to many job offers, sending multiple emails in a short period of time can make the sending behavior look automated and may increase the risk of emails being flagged as spam or blocked by email providers.

Describe the solution you'd like

Add an email sending queue system that schedules application emails and sends them gradually instead of sending all emails immediately.

The system should support:

• Configurable delay between emails.
• Daily sending limits.
• Queue management for pending, sent, and failed emails.
• Retry mechanism for failed sends.
• Ability to pause and resume the sending process.
• Tracking the status of each application email from the CLI and web UI.

Describe alternatives you've considered

• Sending all emails instantly, but this can lead to spam detection or provider restrictions.
• Manually sending each email, but this removes the automation advantage of ApplyWorkflow.
• Using external email automation platforms, which adds unnecessary complexity and dependencies.

Additional context

This feature would make ApplyWorkflow more suitable for real-world job application workflows by providing safer and more natural email sending behavior while keeping the automation benefits.