Added Cleanup Loop/Reaper for Expired TTL VMs

[yulmwu]

Previously, even after a VM's TTL had expired, it remained in the platform database unless manually deleted.

Since this could cause UX issues, this PR adds logic to periodically remove expired VMs from the vms table. By default, the cleanup loop runs every 30 minutes.

The newly added environment variable is as follows:

VM_CLEANUP_INTERVAL=30m

For more details, please refer to the changes included in this PR.

[codecov]

Codecov Report

❌ Patch coverage is 70.17544% with 17 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/service/vm_service.go	65.78%	7 Missing and 6 partials ⚠️
internal/repo/vm_repo.go	66.66%	2 Missing and 2 partials ⚠️

📢 Thoughts on this report? Let us know!

[Copilot]

Pull request overview

This PR adds automatic cleanup for expired VM database rows so stale VM records no longer remain indefinitely after their TTL passes.

Changes:

• Adds VM cleanup configuration via VM_CLEANUP_INTERVAL.
• Adds service/repo cleanup logic plus a background TTL reaper.
• Adds tests and documentation for expired VM row cleanup behavior.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/service/vm_service.go	Adds per-user expired VM cleanup and background TTL reaper logic.
internal/service/vm_service_test.go	Adds service tests for cleanup behavior.
internal/repo/vm_repo.go	Adds bulk deletion of expired VM rows.
internal/repo/vm_repo_test.go	Adds repository coverage for expired-row deletion.
internal/config/config.go	Adds cleanup interval config loading, validation, and logging.
internal/config/config_test.go	Adds config tests for cleanup interval defaults/custom/invalid values.
docs/docs/vms.md	Updates VM documentation for automatic cleanup behavior.
cmd/server/main.go	Starts the VM TTL reaper during server startup.
.env.example	Documents VM_CLEANUP_INTERVAL.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.