fix(test): fix suspend, SDN, container, and OVA integration test failures

- Suspend/Resume: move to Linux VM lifecycle context (empty VMs may
  not reliably transition to paused state)
- SDN subnet model: dhcp-range is an array, not string
- SDN subnet delete: use PVE-format ID (vnet-ip-prefix) not CIDR
- Container config: trim trailing newline from PVE description
- OVA: use qemu-img to create valid sparse VMDK (add qemu-utils to
  test container Dockerfile)
- Enable 'images' content type on local storage for OVA import

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/infrastructure/scripts/prepare-test-environment.sh

@@ -63,8 +63,8 @@ if [ ! -f "${OVA_PATH}" ]; then
     echo "Creating minimal test OVA..."
     OVA_TMPDIR=$(mktemp -d)
 
-    # Create a 1MB raw disk image and convert to vmdk-stream (flat)
-    dd if=/dev/zero of="${OVA_TMPDIR}/test-disk.vmdk" bs=1M count=1 2>/dev/null
+    # Create a minimal valid sparse VMDK using qemu-img
+    qemu-img create -f vmdk -o subformat=streamOptimized "${OVA_TMPDIR}/test-disk.vmdk" 64M 2>/dev/null
 
     # Create OVF descriptor
     cat > "${OVA_TMPDIR}/test-appliance.ovf" <<'OVF'