fix: client-side image type guard and deselect affordance on TrackEdit

DeepDrftManager/Services/CmsTrackService.cs

@@ -241,16 +241,26 @@ public class CmsTrackService : ICmsTrackService
         }
     }
 
+    private static readonly HashSet<string> KnownImageMimeTypes = new(StringComparer.OrdinalIgnoreCase)
+    {
+        "image/jpeg", "image/png", "image/gif", "image/webp", "image/svg+xml", "image/bmp"
+    };
+
     public async Task<ResultContainer<string>> UploadImageAsync(
         Stream imageStream,
         string fileName,
         string contentType,
         CancellationToken ct = default)
     {
+        if (string.IsNullOrWhiteSpace(contentType) || !KnownImageMimeTypes.Contains(contentType))
+        {
+            _logger.LogWarning("UploadImageAsync rejected: unsupported or missing content type '{ContentType}'", contentType);
+            return ResultContainer<string>.CreateFailResult($"Unsupported image type: {contentType}. Accepted: JPEG, PNG, GIF, WebP, SVG, BMP.");
+        }
+
         using var multipart = new MultipartFormDataContent();
         var imageContent = new StreamContent(imageStream);
-        imageContent.Headers.ContentType = new MediaTypeHeaderValue(
-            string.IsNullOrWhiteSpace(contentType) ? "application/octet-stream" : contentType);
+        imageContent.Headers.ContentType = new MediaTypeHeaderValue(contentType);
         multipart.Add(imageContent, "image", fileName);
 
         var client = _httpClientFactory.CreateClient(ContentCmsClientName);