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/autolabeler-config.json

@@ -97,7 +97,7 @@
         {
             "fileStatus": "modified",
             "includeGlobs": [
-                "frontend/public/json/**"
+                "json/**"
             ],
             "excludeGlobs": []
         }