refactor: restructure to monorepo with backends and apiTest

- Move web/backend to backends/potter-api
- Move web/frontend to backends/potter-api/frontend
- Add root package.json with npm workspaces
- Update README.md with monorepo navigation
- Update .github/workflows/api-tests.yml for dynamic test discovery
- Update bruno_test_scenario.md paths
- Fix .gitignore to allow JSON data files
- Add three new AI tests in apiTest/PotterAPI/AI/

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

backends/potter-api/frontend/.gitignore

@@ -0,0 +1,21 @@
+.DS_Store
+node_modules
+/dist
+
+# local env files
+.env.local
+.env.*.local
+
+# Log files
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Editor directories and files
+.idea
+.vscode
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?