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>

backend/package.json

@@ -0,0 +1,56 @@
+{
+  "name": "website-monitoring-backend",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "type": "module",
+  "scripts": {
+    "build": "tsc",
+    "start": "node dist/index.js",
+    "dev": "tsx watch src/index.ts",
+    "test": "NODE_OPTIONS='--experimental-vm-modules' jest --passWithNoTests",
+    "test:coverage": "NODE_OPTIONS='--experimental-vm-modules' jest --coverage",
+    "lint": "eslint src/",
+    "lint:fix": "eslint src/ --fix",
+    "format": "prettier --write src/"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/denshooter/website-monitoring-backend.git"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/denshooter/website-monitoring-backend/issues"
+  },
+  "homepage": "https://github.com/denshooter/website-monitoring-backend#readme",
+  "dependencies": {
+    "chrome-launcher": "^1.1.2",
+    "cors": "^2.8.5",
+    "dotenv": "^16.4.7",
+    "express": "^4.21.2",
+    "lighthouse": "^12.4.0",
+    "lighthouse-logger": "^2.0.1",
+    "pg": "^8.13.3",
+    "ts-node": "^10.9.2",
+    "tsconfig-paths": "^4.2.0",
+    "uuid": "^11.1.0"
+  },
+  "devDependencies": {
+    "@types/cors": "^2.8.17",
+    "@types/express": "^4.17.21",
+    "@types/jest": "^30.0.0",
+    "@types/node": "^22.13.9",
+    "@types/supertest": "^7.2.0",
+    "@typescript-eslint/eslint-plugin": "^8.56.1",
+    "@typescript-eslint/parser": "^8.56.1",
+    "eslint": "^10.0.2",
+    "eslint-config-prettier": "^10.1.8",
+    "jest": "^30.2.0",
+    "prettier": "^3.8.1",
+    "supertest": "^7.2.2",
+    "ts-jest": "^29.4.6",
+    "tsx": "^4.21.0"
+  }
+}