feat: add one-click quick maintenance with auto-disable on UP

[luitelbj]

Summary

In this pull request, the following changes are made:

• Add a Quick Maintenance button on the monitor detail page that puts a monitor into maintenance mode with one click
• Add an End Maintenance button to manually end any active maintenance from the monitor detail page
• Auto-disable maintenance when the service recovers (DOWN --> UP transition), so operators don't need to remember to end maintenance after fixing issues
• Add Auto-end when service is UP checkbox to the EditMaintenance form (manual strategy only)
• Add auto-disable badge on the Manage Maintenance page

Relates to #2984 #3768 #5499

Please follow this checklist to avoid unnecessary back and forth (click to expand)

• ⚠️ If there are Breaking change (a fix or feature that alters existing functionality in a way that could cause issues) I have called them out
• 🧠 I have disclosed any use of LLMs/AI in this contribution and reviewed all generated content.
  I understand that I am responsible for and able to explain every line of code I submit.
• 🔍 Any UI changes adhere to visual style of this project.
• 🛠️ I have self-reviewed and self-tested my code to ensure it works as expected.
• 📝 I have commented my code, especially in hard-to-understand areas (e.g., using JSDoc for methods).
• 🤖 I added or updated automated tests where appropriate.
• 📄 Documentation updates are included (if applicable).
• 🧰 Dependency updates are listed and explained.
• ⚠️ CI passes and is green.

How It Works

Quick Maintenance button: Creates a manual strategy maintenance with auto_disable_on_up = true, linked to the monitor. The heartbeat loop continues running actual checks instead of skipping them.

Auto-disable logic: During each heartbeat, if the monitor is under an auto-disable maintenance, the actual health check still runs. The result is tracked via lastActualStatus. When the check detects a DOWN → UP transition, the maintenance is automatically ended and the frontend is updated via socket in real-time. If the service was never DOWN, maintenance stays active until manually ended.

End Maintenance button: Works for any active maintenance type (not just quick maintenances), allowing operators to end maintenance directly from the monitor detail page.

Dependencies

No new dependencies added.

AI Disclosure

Claude Code was used during the implementation to assist with parts of the development. All code has been reviewed, understood, and tested.

Screenshots for Visual Changes

• UI Modifications: Added "Quick Maintenance" and "End Maintenance" buttons to monitor detail page. Added auto-disable checkbox to EditMaintenance form. Added auto-disable badge to Manage Maintenance list.

Event	Before	After
Monitor active
Edit maintenance
Under Maintenance
Manage Maintenance

This is my first contribution to Uptime Kuma, looking forward to feedback and happy to make any adjustments.

[github-actions]

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