Fix Drive video upload to Shopify

- Detect video mime types in MediaService to set correct resource ('VIDEO') and mediaContentType.

- Add fileSize to stagedUploadsCreate payload as required by Shopify for videos.

- Add safety check for missing upload targets to prevent crashes.

- Implement getSize in MockDriveService.

- Add unit test in MediaService.test.ts to verify correct resource and fileSize handling for video uploads.

- Update mock in mediaManager.integration.test.ts to support getSize().

src/services/MediaService.test.ts

@@ -163,4 +163,46 @@ describe("MediaService Robust Sync", () => {
       expect(spyRename).toHaveBeenCalledWith(f1.getId(), expect.stringMatching(/^SKU123_\d+\.jpg$/))
       expect(spyRename).not.toHaveBeenCalledWith(f2.getId(), expect.anything())
   })
+  test("Upload: Handles Video Uploads with correct resource type", () => {
+    const folder = driveService.getOrCreateFolder("SKU_VIDEO", "root")
+
+    // Mock Video Blob
+    const videoBlob = {
+        getName: () => "video.mp4",
+        getBytes: () => [],
+        getContentType: () => "video/mp4",
+        getThumbnail: () => ({ getBytes: () => [] })
+    } as any
+
+    const vidFile = driveService.saveFile(videoBlob, folder.getId())
+
+    const finalState = [{
+        id: vidFile.getId(),
+        driveId: vidFile.getId(),
+        filename: "video.mp4",
+        source: "drive_only"
+    }]
+
+    const spyStaged = jest.spyOn(shopifyService, 'stagedUploadsCreate')
+    const spyCreate = jest.spyOn(shopifyService, 'productCreateMedia')
+
+    mediaService.processMediaChanges("SKU_VIDEO", finalState, "pid")
+
+    // 1. Verify stagedUploadsCreate called with resource="VIDEO" and fileSize
+    expect(spyStaged).toHaveBeenCalledWith(expect.arrayContaining([
+        expect.objectContaining({
+            resource: "VIDEO",
+            mimeType: "video/mp4",
+            filename: "video.mp4",
+            fileSize: "0" // 0 because mock bytes are empty
+        })
+    ]))
+
+    // 2. Verify productCreateMedia called with mediaContentType="VIDEO"
+    expect(spyCreate).toHaveBeenCalledWith("pid", expect.arrayContaining([
+        expect.objectContaining({
+            mediaContentType: "VIDEO"
+        })
+    ]))
+  })
 })