feat(system-service): add PM2 picker and platform selection

[KraoESPfan1n]

Summary

In this pull request, the following changes are made:

• Add explicit PM2 support to the system-service monitor, including Windows-compatible PM2 execution.

• Add configurable platform selection for system services (Linux / Windows Server) in monitor UI.

• Add PM2 process picker in monitor UI (socket-driven process list + refresh).

• Keep backward compatibility with existing system_service_name values.

• Add backend tests for PM2 state mapping and platform selection routing.

• Relates to Monitor pm2 #3011

• Related discussion: Monitor pm2 #3011 (comment)

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.

Screenshots for Visual Changes

• UI changes in Edit Monitor for System Service / PM2 configuration and PM2 process selection.
• No screenshot attached in this CLI submission.

[github-actions]

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[KraoESPfan1n]

closed to upload an updated version