fix: download button now fetches blob and triggers actual file download

Previously the download link just navigated cross-origin to the media URL.
Now uses JS interop to fetch the file as a blob, create an object URL,
and trigger a browser download via a hidden anchor element.

MilkStream.Client/Components/Pages/Home.razor

@@ -101,10 +101,10 @@
                            title="View full size" @onclick:stopPropagation="true">
                             <i class="bi bi-arrows-fullscreen"></i>
                         </a>
-                        <a class="preview-action-btn" href="@OriginalUrl(selectedAsset.Id)" download
-                           title="Download" @onclick:stopPropagation="true">
+                        <button class="preview-action-btn" @onclick="() => DownloadOriginal(selectedAsset.Id)"
+                                @onclick:stopPropagation="true" title="Download">
                             <i class="bi bi-download"></i>
-                        </a>
+                        </button>
                     </div>
                 </div>
             </div>
@@ -217,6 +217,10 @@
         }
     }
 
+    async Task DownloadOriginal(Guid id) {
+        await jsRuntime.InvokeVoidAsync("masonryObserver.downloadFile", OriginalUrl(id));
+    }
+
     static string GetAspectRatio(AssetPreviewDto asset) {
         if (asset.ResolutionWidth > 0 && asset.ResolutionHeight > 0)
             return $"{asset.ResolutionWidth} / {asset.ResolutionHeight}";

MilkStream.Client/Components/Pages/Home.razor.css

@@ -204,6 +204,9 @@
     transition: color 0.15s;
     display: flex;
     align-items: center;
+    background: none;
+    border: none;
+    cursor: pointer;
 }
 
 .preview-action-btn:hover {

MilkStream.Client/wwwroot/js/masonryObserver.js

@@ -30,5 +30,18 @@ window.masonryObserver = {
 
     unlockBodyScroll: function () {
         document.body.style.overflow = '';
+    },
+
+    downloadFile: async function (url) {
+        const response = await fetch(url);
+        const blob = await response.blob();
+        const blobUrl = URL.createObjectURL(blob);
+        const a = document.createElement('a');
+        a.href = blobUrl;
+        a.download = '';
+        document.body.appendChild(a);
+        a.click();
+        document.body.removeChild(a);
+        URL.revokeObjectURL(blobUrl);
     }
 };