Cleaned frontend config to use yarn

.gitignore

@@ -21,12 +21,15 @@ Thumbs.db
 
 # Node / frontend
 frontend/node_modules/
+frontend/.yarn/
 frontend/dist/
 frontend/build/
 frontend/.cache/
 frontend/.vite/
 frontend/.turbo/
 frontend/.eslintcache
+package-lock.json
+npm-shrinkwrap.json
 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*

docs/3_guidelines/development-guidelines.md

@@ -1403,6 +1403,7 @@ docker-compose up -d
 ```
 
 ### Frontend Development
+Note: This project uses Yarn with `nodeLinker: node-modules`. PnP files like `.pnp.cjs` and `.pnp.loader.mjs` are not used.
 ```bash
 # Web application
 cd frontend/apps/web

docs/4_work_plan/1.1-development-environment-setup.md

@@ -752,6 +752,7 @@ docker-compose logs postgres
   "packageManager": "yarn@4.0.0"
 }
 ```
+Note: Yarn is configured to use `nodeLinker: node-modules` (no PnP files).
 
 #### 1.5.2 Web Application Package