Fix Shopify video previews and various improvements

- Ensure Shopify video sync updates Media Manager with active video previews
- Fix "Image load failed" error for video icons by using Base64 SVG
- Resolve Drive picker origin error by using google.script.host.origin
- Fix Drive video playback issues by using Drive iframe player
- Add `test:log` script to package.json for full output logging in Windows
- Update .gitignore to exclude coverage, test_output.txt, and .agent/
- Remove test_output.txt from git tracking

package.json

@@ -9,6 +9,7 @@
     "build": "webpack --mode production",
     "deploy": "clasp push",
     "test": "jest",
+    "test:log": "jest > test_output.txt 2>&1",
     "prepare": "husky"
   },
   "devDependencies": {