refactor: flatten monorepo structure to backend/ frontend/ devops/

Rename subdirectories for a cleaner single-repo layout:
- website-monitoring-backend/  → backend/
- website-monitoring-frontend/ → frontend/
- website-monitoring-devops/   → devops/

Update all references in package.json scripts, CI workflows,
docker-compose, pre-commit hooks, and documentation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/scanner-worker/package.json

@@ -0,0 +1,23 @@
+{
+  "name": "scanner-worker",
+  "version": "1.0.0",
+  "main": "express-worker.ts",
+  "scripts": {
+    "start": "ts-node express-worker.ts"
+  },
+  "dependencies": {
+    "@supabase/supabase-js": "^2.50.0",
+    "chrome-launcher": "^0.15.0",
+    "cors": "^2.8.5",
+    "dotenv": "^16.5.0",
+    "express": "^4.18.2",
+    "lighthouse": "^12.6.1"
+  },
+  "devDependencies": {
+    "@types/cors": "^2.8.19",
+    "@types/express": "^4.17.21",
+    "@types/node": "^20.0.0",
+    "ts-node": "^10.9.1",
+    "typescript": "^5.0.0"
+  }
+}