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/sortinghatquotes.json

@@ -0,0 +1,9 @@
+[
+    "Move your ass to",
+    "You are a coward without future, your house is",
+    "Your broom is too magnificent, you should study at",
+    "Oh shit, that's right I'm a hat. And your house is",
+    "Stick your wand into",
+    "Hmm, difficult. VERY difficult. Plenty of courage, I see. But where to put you? All right it's",
+    "I'm just a hat. My only task is to pick random house..Like this one."
+]