feat(docker): add HTTP Basic Authentication support

[enixCode]

Changes

• .env.example - Document new environment variables
• Dockerfile - Install openssl for password hashing
• docker-entrypoint.sh - Generate .htpasswd dynamically
• nginx.conf - Configure auth_basic conditionally
• compose.yml / compose.dev.yml - Add environment variables
• .dockerignore - New file for cleaner builds
• README.md - Document the feature

Usage

  # Enable authentication
  HTTP_AUTH_USER=admin HTTP_AUTH_PASSWORD=secret docker compose up

Test plan

• Without auth variables → App accessible (200 OK)
• With auth, no credentials → 401 Unauthorized
• With auth + correct credentials → 200 OK

Closes #174