docs: [#272] add comprehensive HTTPS support specification with Caddy

- Create detailed issue specification for HTTPS implementation
- Document service-based TLS architecture with configuration examples
- Include implementation phases, acceptance criteria, and ADRs
- Add configurable Let's Encrypt staging environment support
- Link issue #272 to roadmap section 6.1
- Reference production deployment and security evaluation (#270)

Issue: #272

Author: josecelano