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.ts

@@ -277,7 +277,8 @@ export class MediaService {
              return {
                  filename: f.getName(),
                  mimeType: f.getMimeType(),
-                 resource: "IMAGE",
+                 resource: f.getMimeType().startsWith('video/') ? "VIDEO" : "IMAGE",
+                 fileSize: f.getSize().toString(),
                  httpMethod: "POST",
                  file: f,
                  originalItem: item
@@ -290,14 +291,26 @@ export class MediaService {
             filename: u.filename,
             mimeType: u.mimeType,
             resource: u.resource,
+            fileSize: u.fileSize,
             httpMethod: u.httpMethod
         }))
         const stagedResp = shopifySvc.stagedUploadsCreate(stagedInput)
+
+        if (stagedResp.userErrors && stagedResp.userErrors.length > 0) {
+             console.error("[MediaService] stagedUploadsCreate Errors:", JSON.stringify(stagedResp.userErrors))
+             logs.push(`- Upload preparation failed: ${stagedResp.userErrors.map(e => e.message).join(', ')}`)
+        }
+
         const targets = stagedResp.stagedTargets
 
         const mediaToCreate = []
         uploads.forEach((u, i) => {
             const target = targets[i]
+            if (!target || !target.url) {
+                logs.push(`- Failed to get upload target for ${u.filename}: Invalid target`)
+                console.warn(`[MediaService] Missing target URL for ${u.filename}. Target:`, JSON.stringify(target))
+                return
+            }
             const payload = {}
             target.parameters.forEach((p: any) => payload[p.name] = p.value)
             payload['file'] = u.file.getBlob()
@@ -305,7 +318,7 @@ export class MediaService {
             mediaToCreate.push({
                 originalSource: target.resourceUrl,
                 alt: u.filename,
-                mediaContentType: "IMAGE"
+                mediaContentType: u.resource
             })
         })