CUB-10: Create IMoonrakerClient interface and DTOs

- Expanded IMoonrakerClient interface with 6 strongly-typed methods:
  - GetServerInfoAsync (Moonraker /server/info)
  - IsReachableAsync (connectivity check)
  - GetPrinterInfoAsync (Moonraker /printer/info)
  - GetPrintHistoryAsync (Moonraker /server/history/items)
  - GetPrintStatsAsync (Moonraker /printer/objects/query?print_stats)
  - GetDisplayStatusAsync (Moonraker /printer/objects/query?display_status)
  - GetFilamentUsageAsync (retained for backward compatibility)

- Created Domain/DTOs/Moonraker/ with 7 DTOs:
  - MoonrakerServerInfo, MoonrakerPrinterInfo, MoonrakerPrintJob
  - MoonrakerHistoryResponse, MoonrakerPrintStats
  - MoonrakerDisplayStatus, MoonrakerRequest

- Updated MoonrakerClient implementation to support all new methods
  with proper JSON parsing and mapping helpers

- Full XML doc comments on all public members

backend/Domain/DTOs/Moonraker/MoonrakerPrintStats.cs

@@ -0,0 +1,36 @@
+namespace Extrudex.Domain.DTOs.Moonraker;
+
+/// <summary>
+/// Response DTO for Moonraker /printer/objects/query?print_stats endpoint.
+/// Contains real-time print statistics including current job state,
+    /// filament consumed, and file being printed.
+/// </summary>
+public class MoonrakerPrintStats
+{
+    /// <summary>
+    /// Current print state: "standby", "printing", "paused", "complete", "error", "cancelled".
+    /// </summary>
+    public string State { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Total filament used in millimeters for the current print session.
+    /// </summary>
+    public decimal FilamentUsedMm { get; set; }
+
+    /// <summary>
+    /// Total print duration in seconds for the current print session.
+    /// </summary>
+    public decimal PrintDurationSeconds { get; set; }
+
+    /// <summary>
+    /// Filename of the G-code file currently being printed.
+    /// Null if no print is active.
+    /// </summary>
+    public string? Filename { get; set; }
+
+    /// <summary>
+    /// Detailed message from Klipper about the current print state.
+    /// May contain error details when state is "error".
+    /// </summary>
+    public string? Message { get; set; }
+}