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)

.gitattributes

@@ -10,11 +10,6 @@
 # Treat Golang files as Go (for /api/)
 api/**/*.go linguist-language=Go
 
-# ---------------------------------------
-# Treat frontend as JavaScript/TypeScript (optional)
-frontend/**/*.ts linguist-language=TypeScript
-frontend/**/*.js linguist-language=JavaScript
-
 # ---------------------------------------
 # Exclude documentation from stats
 *.md linguist-documentation
@@ -26,7 +21,7 @@ SECURITY.md linguist-documentation
 # ---------------------------------------
 # Exclude generated/config files
 *.json linguist-generated
-frontend/public/json/*.json linguist-generated=false
+json/*.json linguist-generated=false
 *.lock linguist-generated
 *.yml linguist-generated
 *.yaml linguist-generated