refactor: move json/ to top-level, remove frontend/, update workflows

- Move frontend/public/json/ to json/ (top-level)
- Update all workflow path references to json/
- Delete frontend-cicd.yml workflow
- Delete frontend/ directory entirely
- Clean up .gitattributes (remove frontend entries)

.github/workflows/scripts/get-gh-release.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 INPUT_FILE=".github/workflows/scripts/repos.txt"
-OUTPUT_FILE="frontend/public/json/versions.json"
+OUTPUT_FILE="json/versions.json"
 TMP_FILE="releases_tmp.json"
 
 if [ -f "$OUTPUT_FILE" ]; then