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>

src/PSProxmoxVE.Core/Models/Network/PveSdnSubnet.cs

@@ -46,11 +46,11 @@ public class PveSdnSubnet
     public string? DnsZonePrefix { get; set; }
 
     /// <summary>
-    /// The DHCP range configuration for automatic IP assignment.
+    /// The DHCP range configurations for automatic IP assignment.
     /// </summary>
     [JsonPropertyName("dhcp-range")]
     [JsonProperty("dhcp-range")]
-    public string? DhcpRange { get; set; }
+    public string[]? DhcpRanges { get; set; }
 
     /// <summary>
     /// The subnet type identifier used internally by PVE.