feat: initialize monorepo with full dev team best practices

- Unified monorepo with backend (Express), frontend (Next.js), and devops
- Backend: ESLint, Prettier, Jest tests (3 passing), health endpoint, .env.example
- Frontend: Fixed build errors, fixed all lint errors (0 remaining), tests passing
- DevOps: Docker Compose with PostgreSQL, backend, frontend + healthchecks
- CI/CD: 3 GitHub Actions workflows (backend, frontend, docker integration)
- DX: Husky pre-commit hooks with smart change detection
- Docs: Root README with architecture, CONTRIBUTING.md, PR template

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

website-monitoring-backend/Dockerfile

@@ -0,0 +1,25 @@
+# Use the official Node.js image.
+FROM node:18
+
+# OPTIONAL: Falls in der Base kein Chrome enthalten ist,
+# müsstest du hier noch "apt-get update" + "apt-get install chromium" oder ähnliches ausführen,
+# z. B.:
+RUN apt-get update && apt-get install -y chromium
+
+# Create and change to the app directory.
+WORKDIR /app
+
+# Copy application dependency manifests to the container image.
+COPY package*.json ./
+
+# Install production dependencies.
+RUN npm install
+
+# Copy local code to the container image.
+COPY . .
+
+# Build the TypeScript code
+RUN npm run build
+
+# Run the web service on container startup.
+CMD ["node", "dist/index.js"]