feat: add new features including SEO, sitemap, and subjects management

- Create robots.txt to allow search engine indexing and specify sitemap location.
- Implement ajouterSujet.js for adding new subjects to sujets.json.
- Develop dynamic subject pages in page.tsx using static generation with metadata.
- Add contact, error, not found, and privacy policy pages for improved user experience.
- Generate sitemap.xml for better search engine visibility.
- Create SEO component for managing page metadata.
- Populate sujets.json with detailed subject information for dynamic content rendering.

docker-compose.yml

@@ -0,0 +1,10 @@
+services:
+  nextjs-app:
+    image: node:20
+    working_dir: /app
+    volumes:
+      - ./:/app
+    command: sh -c "npm install && npm run build && npm run start"
+    ports:
+      - "3003:3000"
+    restart: unless-stopped