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/jest.config.ts

@@ -0,0 +1,15 @@
+import nextJest from 'next/jest.js';
+
+const createJestConfig = nextJest({
+  dir: './',
+});
+
+const customJestConfig = {
+  testEnvironment: 'jsdom',
+  moduleNameMapper: {
+    '^@/(.*)$': '<rootDir>/src/$1',
+  },
+  setupFilesAfterEnv: ['<rootDir>/jest.setup.ts'],
+};
+
+export default createJestConfig(customJestConfig);