[KVM] Restored backup volume not attached to running VM via libvirt - only database updated

### problem

## Description
When restoring a volume from backup and attaching it to a **running** KVM VM, the volume is only attached at the **database level** but not actually hot-attached to the running VM via libvirt. This means:
1. The volume appears in CloudStack UI as "attached"
2. The volume does NOT appear in `virsh domblklist `
3. The volume is NOT visible inside the guest OS
4. User must reboot(forced) the VM to see the restored volume
## Root Cause
In `KVMGuru.attachRestoredVolumeToVirtualMachine()` (line 380-400), the method only:
- Updates the volume state in the database via `_volumeDao.attachVolume()`
- Sets volume state to `Ready`
It does **NOT**:
- Check if VM is running
- Send an `AttachCommand` to the KVM agent to hot-attach the disk via libvirt
## Expected Behavior
When attaching a restored volume to a **running** VM:
1. CloudStack should detect the VM state
2. If VM is [Running](cci:1://file:///root/new_merge/olympos-cloud-platform/plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtComputingResource.java:5982:4-5991:5), send a libvirt attach command to hot-attach the disk
3. Volume should immediately appear in `virsh domblklist` and inside guest OS
4. No reboot should be required

### versions

CloudStack: 4.21.0
Hypervisor: KVM
Host OS: Rocky Linux 9
Guest OS: Rocky Linux 9 / Windows 10 - 2022 Server

### The steps to reproduce the bug

## Steps to Reproduce
1. Create a VM with a data disk
2. Create a backup of the VM
3. Start the VM (ensure it's running)
4. Restore the backed-up volume and attach to the running VM via API:
`restoreVolumeFromBackupAndAttachToVM`
5. Check `virsh domblklist ` on the KVM host
6. **Observe:** The restored volume is NOT listed
7. Check inside guest OS
8. **Observe:** The disk is NOT visible
9. Reboot(forced) the VM
10. **Observe:** After reboot(forced), the disk appears

### What to do about it?

Either:
A) Add hot-attach logic to `KVMGuru.attachRestoredVolumeToVirtualMachine()` to send `AttachCommand` when VM is running
B) Or document this as expected behavior and require users to stop VM before restoring volumes
Option A is preferred as it aligns with how regular [attachVolume](cci:1://file:///root/new_merge/olympos-cloud-platform/server/src/main/java/com/cloud/storage/VolumeApiServiceImpl.java:2479:4-2483:5) API works for running VMs.

Commencez dans KVMGuru.attachRestoredVolumeToVirtualMachine(), en particulier aux lignes citées, et comparez son rattachement en base de données avec le chemin normal de l’API attachVolume. Examinez la gestion de l’état d’exécution dans LibvirtComputingResource ainsi que le flux de AttachCommand. Reproduisez restoreVolumeFromBackupAndAttachToVM avec une VM en cours d’exécution, puis vérifiez que le disque restauré apparaît dans virsh domblklist et dans le guest sans redémarrage.

Rédigé par le modèle d'indexation à partir du texte de l'issue.