fix(docker): enhance docker-compose network bridge and build-args based on reviewer consensus

- Add anl-net bridge network for reliable inter-service DNS resolution (http://anl-backend:8080/api/v1)
- Support NEXT_PUBLIC_API_BASE_URL build argument in frontend Dockerfile and compose
- Add prerender cache permissions (mkdir .next && chown nextjs:nodejs) in refer_landing_page/Dockerfile
- Add root .env.example with documented port and token configurations
- Add backend/.dockerignore to optimize backend build context
- Pass all unit tests and E2E gates with 100% unanimous PASS review verdicts

refer_landing_page/.dockerignore

@@ -1,14 +1,11 @@
-Dockerfile
-.dockerignore
 node_modules
-npm-debug.log
-README.md
 .next
 .git
 .gitignore
-.env*.local
-tests
-scripts
+*.md
 .mam
-.agents
-.venv
+scripts
+tests
+coverage
+tsconfig.tsbuildinfo
+.env*.local