Add ArteryTek AT32 DFU bootloader support

VID 0x2E3C / PID 0xDF11, flashed via dfu-util with address 0x08000000.
Mirrors PR qmk#482.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tzarc

src/QmkToolbox.Core/Bootloader/BootloaderFactory.cs

@@ -91,6 +91,9 @@ private static BootloaderType QmkOrLufaHid(ushort rev) =>
         // ── GigaDevice Semiconductor (0x28E9) ──────────────────────────
         [(0x28E9, 0x0189)] = new(BootloaderType.Gd32VDfu),
 
+        // ── ArteryTek (0x2E3C) ──────────────────────────────────────────
+        [(0x2E3C, 0xDF11)] = new(BootloaderType.At32Dfu),
+
         // ── Geehy Semiconductor (0x314B) ────────────────────────────────
         [(0x314B, 0x0106)] = new(BootloaderType.Apm32Dfu),
 
@@ -111,6 +114,7 @@ public static IUsbDevice CreateDevice(
         return GetDeviceType(device.VendorId, device.ProductId, device.RevisionBcd) switch
         {
             BootloaderType.Apm32Dfu => new Apm32DfuDevice(device, toolProvider),
+            BootloaderType.At32Dfu => new At32DfuDevice(device, toolProvider),
             BootloaderType.AtmelDfu => new AtmelDfuDevice(device, toolProvider, serialPortService),
             BootloaderType.AtmelSamBa => new AtmelSamBaDevice(device, toolProvider, serialPortService),
             BootloaderType.AvrIsp => new AvrIspDevice(device, toolProvider, serialPortService),

src/QmkToolbox.Core/Bootloader/Impl/At32DfuDevice.cs

@@ -0,0 +1,12 @@
+using QmkToolbox.Core.Models;
+using QmkToolbox.Core.Services;
+
+namespace QmkToolbox.Core.Bootloader.Impl;
+
+/// <summary>ArteryTek AT32 DFU bootloader device (via dfu-util).</summary>
+internal sealed class At32DfuDevice(IUsbDevice device, IFlashToolProvider toolProvider)
+    : DfuUtilDevice(device, toolProvider,
+        BootloaderType.At32Dfu, "ArteryTek AT32 DFU",
+        altSetting: 0, deviceId: "2E3C:DF11",
+        flashSuffix: "-s 0x08000000:leave",
+        resetSuffix: "-s 0x08000000:leave");

src/QmkToolbox.Core/Models/BootloaderType.cs

@@ -4,6 +4,7 @@ namespace QmkToolbox.Core.Models;
 public enum BootloaderType
 {
     Apm32Dfu,
+    At32Dfu,
     AtmelDfu,
     AtmelSamBa,
     AvrIsp,