fix: convert cf-kv and excalidraw-libraries from submodules to regular files

- Remove stale cloudflare-worker submodule entry from .gitmodules
- Remove .git dirs from cf-kv and excalidraw-libraries so Git tracks them as regular files
- Fixes 'No url found for submodule path cf-kv' CI error

excalidraw-libraries/.gitignore

@@ -0,0 +1,8 @@
+ __pycache__
+.DS_Store
+*.pyc
+*key.json
+node_modules
+yarn-error.log
+venv
+.vscode