[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.

Beginnen Sie in KVMGuru.attachRestoredVolumeToVirtualMachine(), insbesondere bei den genannten Zeilen, und vergleichen Sie dessen Datenbank-Anbindung mit dem regulären attachVolume-API-Pfad. Lesen Sie die Behandlung des laufenden Zustands in LibvirtComputingResource und den Ablauf von AttachCommand. Stellen Sie restoreVolumeFromBackupAndAttachToVM mit einer laufenden VM nach und überprüfen Sie anschließend, dass die wiederhergestellte Festplatte in virsh domblklist und im Gast ohne Neustart erscheint.

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